Strengthen and Weaken: The Right Answer Doesn't Have to PROVE Anything

By EMPOWERgmat on October 20, 2020

You are down to two answers on a Weaken question. One of them makes you think, "Sure, but that doesn't PROVE the argument is wrong." So you cross it off. You pick the other one because it sounds bigger and bolder. Then you check the answer key, and the one you crossed off was right.

I watch Test Takers do this every single week. It is one of the most common ways people lose points in Critical Reasoning. The fix is not more practice questions. The fix is changing ONE belief you are carrying into these questions.

Here it is: on Strengthen and Weaken questions, the right answer does not have to prove anything. It only has to nudge the argument. A little push. That's it.

What these questions actually ask

Quick setup. Critical Reasoning (CR) is one of the three question types in the GMAT Verbal section, which gives you 36 questions in 65 minutes. Each CR question gives you a short argument. An argument has a conclusion (the claim the author wants you to believe) and premises (the facts used to support it). Between them is a gap, and the author fills that gap with an unstated assumption.

A Strengthen question asks which answer, if true, makes the conclusion MORE likely. A Weaken question asks which answer, if true, makes the conclusion LESS likely. Read those words again. More likely. Less likely. Not "proves." Not "destroys." Not "settles the matter forever."

And notice the two words "if true." You are told to accept each answer as a fact. You do not get to argue with it. Your only job is to ask what that new fact does to the conclusion.

A balance scale holding two equal weights, with a single small feather resting on one side so the scale tips only slightly. — The right answer is the feather, not the anvil.

Why the 'proof' instinct kills you

Stop reading for a second and think about this. Why would a smart person cross off an answer that helps?

Because school trained you to look for certainty. In a math class, an answer is right or wrong, done. So when you read a CR answer that only makes the conclusion a bit more or less believable, it feels flimsy. You think there must be something better. There usually isn't. The test writers build the right answer to be modest on purpose, and they build the wrong answers to sound dramatic on purpose.

So you have to decide what you want MORE: an answer that feels airtight, or the right answer. On these questions, you rarely get both.

Let's see it in action.

Try it

In January, the city of Marston replaced the streetlights on Elm Avenue with much brighter ones. In the six months that followed, reported car break-ins on Elm Avenue were far lower than in the same six months of the year before. The city council concludes that the brighter lights caused the drop in break-ins and plans to install them across the whole city.

Which of the following, if true, most seriously weakens the council's conclusion?

The brighter streetlights cost more to run each month than the old ones.
In February, the police began sending two extra night patrols down Elm Avenue.
Several Elm Avenue residents complained that the new lights shine into their bedrooms.
Car break-ins fell in other cities after those cities installed brighter lights.
Most car break-ins on Elm Avenue in past years happened after dark.

Show the answer

Step 1: Notes on paper. Write the conclusion in shorthand: "Bright lights CAUSED fewer break-ins." When you see the word "caused" or anything like it, write down the question every cause argument begs: "Could something ELSE explain the drop?"

Step 2: Mark each answer. Write W (weakens), S (strengthens) or 0 (does nothing) next to each letter.

(A) Cost is about the plan's price, not whether the lights cut break-ins. 0.

(B) Extra police patrols started at nearly the same time. That's another possible cause of the drop. W.

(D) Similar results elsewhere make the lights look MORE effective. S. Wrong direction.

(E) If most break-ins happen in the dark, lights are a sensible fix. If anything, S.

Step 3: Pick. The only W is (B). The answer is B.

The trap: lots of people read (B) and think, "But the lights could STILL have helped. Maybe it was both." True! (B) does not prove the lights did nothing. It doesn't need to. It gives a second explanation for the drop, so the council's claim that the lights caused it becomes less certain. That's a weaken. Notice too that (B) had to be true for the right months. Patrols starting in February overlap the six months after January, so the timing works.

Here's my wager. If you go back through the CR questions you missed last month, I'll bet at least one of them had a right answer you crossed off in your first pass because it "didn't prove anything." Go look. I'll wait.

The same trap, the other direction

Strengthen questions have the exact same problem, just flipped. The right answer often doesn't add new evidence that the conclusion is true. Often, it just shuts down one alternative explanation. That feels small. It's still a strengthen.

Try it

Since a bakery owner began handing out free samples at her front door, her weekday sales have risen. She concludes that the free samples are drawing in new customers.

Which of the following, if true, most strongly supports her conclusion?

During that same period, the bakery did not lower its prices or change its menu.
Many other bakeries in the region also hand out free samples.
Some people who took a free sample did not buy anything.
The free samples cost the bakery a small amount each day.
The bakery's weekday sales had also risen in each of the three years before.

Show the answer

Step 1: Notes. "Samples CAUSED more weekday sales." Again, a cause claim. What else could explain more sales? Lower prices, a new menu, a trend that was already happening.

Step 2: Mark each answer.

(A) Prices and menu stayed the same. Two other explanations are gone. S.

(B) What other bakeries do tells us nothing about this bakery's sales. 0.

(D) Cost is not about whether samples bring in customers. 0.

(E) Sales were already climbing every year. That's an alternative explanation. W.

Step 3: Pick. The answer is A.

The trap: people cross off (A) because "prices staying the same doesn't show the samples worked." Correct, it doesn't SHOW that. But by removing two rival causes, it makes the owner's explanation more likely. A nudge in the right direction is all you need.

The mistakes I see every week

Crossing off an answer because it doesn't prove the conclusion. INSTEAD: ask only one question of each answer. Does this, if true, make the conclusion more likely, less likely, or neither? Mark S, W or 0 on paper, and move on.
Arguing with the answer choice. "But maybe the patrols didn't really go out every night." Stop. You were told "if true." INSTEAD: treat every answer as a fact, no matter how odd it sounds.
Falling for the dramatic answer. Big, sweeping answers feel powerful, but they often attack something the argument never claimed. INSTEAD: tie every answer back to the exact conclusion you wrote down. If it doesn't touch that sentence, it's a 0.
Doing it all 'in your head'. You read five answers, hold three half-thoughts in your memory, then reread the argument twice. That's where your time goes. INSTEAD: write the conclusion in shorthand before you read the answers, and mark every answer as you go. The notes take seconds. Rereading takes minutes.
Forgetting the cause question. A huge share of these arguments claim that one thing caused another. INSTEAD: any time you see a cause claim, write "something else?" on your pad. Weakeners tend to give you that something else. Strengtheners tend to take it away.
Picking the 'best' answer by feel when two remain. INSTEAD: if two answers both seem to work, check direction first (one may strengthen on a Weaken question) and then check scope (one may be about a different group, place or time than the conclusion).

A path splitting into two branches, with a small hand-drawn roadblock placed on one branch so a traveler is steered down the other. — Blocking another explanation is a strengthen, even though it adds nothing new.

Why this matters more than it seems

The Verbal section is adaptive question by question, and you cannot go back to change an answer. So every "I talked myself out of the right answer" moment is locked in the second you click Next. Those are not hard questions you are missing. Those are GETTABLE questions you are giving away, and the gettable ones are where most of your missing points live. If you want the bigger picture on handling the section, read how to crush the Verbal section of the GMAT.

This is also a pride issue, and I'll say it plainly. Some Test Takers believe they're "good at arguing," so they treat CR like a debate they need to win. That instinct makes you hunt for a knockout punch. The GMAT doesn't reward knockouts here. It rewards the person who can calmly say, "This answer moves the conclusion a little in the right direction, so it's the one." The top scorers think this way on purpose, which is a big part of what GMAT assassins do to score at the highest levels.

Don't get too down on yourself if you see this habit in your own work. It's a habit, not a talent problem. Habits can be trained out.

Your challenge for today

Pull up the last 10 Strengthen or Weaken questions you got wrong. Use official practice questions if you have them. For each one, write down, in one sentence, WHY you crossed off the right answer. Be honest. Then count how many of those sentences boil down to "it didn't prove it."

Then redo all 10 with a pen in your hand. Conclusion in shorthand first. S, W or 0 next to every letter. No answer gets crossed off for being too modest. Today, not next week.