Tricky Test 2 Level 58

Overview

The riddle reads: "A pencil and an rubber cost $1.10 together. The pencil costs $1.00 more than the rubber. How much does the rubber cost?" Two answer buttons are shown: $0.05 and $0.10. This is a classic algebra word problem. Let rubber = x, pencil = x + 1.00. Together: x + (x + 1.00) = 1.10, so 2x = 0.10, x = 0.05. The rubber costs $0.05. Tap the $0.05 button.

• Difficulty: Easy
• Estimated moves: 1 tap

Step-by-Step Solution

1. Read the problem: pencil + rubber = $1.10. Pencil costs $1.00 more than the rubber. Find the price of the rubber.
2. Do NOT jump to the intuitive answer of $0.10 — that is the common trap. If the rubber were $0.10, the pencil would be $1.10, and together they would cost $1.20, not $1.10.
3. Set up the algebra. Let r = price of the rubber.
4. The pencil costs r + 1.00.
5. Together they cost: r + (r + 1.00) = 1.10.
6. Simplify: 2r + 1.00 = 1.10.
7. Subtract 1.00: 2r = 0.10.
8. Divide by 2: r = 0.05.
9. The rubber costs $0.05. The pencil therefore costs $1.05. Check: $1.05 + $0.05 = $1.10, and $1.05 is exactly $1.00 more than $0.05. Correct.
10. Tap the left button labeled "$0.05". The level clears.

Strategy & Reasoning

This is one of the most famous "brain teaser" math problems. The intuitive answer that most people blurt out is $0.10, but that is wrong because it makes the total $1.20. The correct answer requires setting up two equations and solving. The puzzle offers only two choices, so if you can eliminate $0.10 by checking it, $0.05 is the only remaining option. The game's hint also nudges you to "Rotate" (i.e. think again / turn the problem over), reinforcing that the obvious answer is a trap. The wording "an rubber" is intentionally slightly off grammar, but that is flavor text and does not change the math.

Tips & Common Mistakes

• Mistake: Tapping $0.10 because it feels like the obvious split. Correct approach: check your work — $0.10 rubber + $1.10 pencil = $1.20 total, which contradicts the $1.10 given.
• Mistake: Trying to rotate the device instead of doing math. Correct approach: the "Rotate" hint is a nudge to reconsider, not a motion control; solve the algebra.
• Mistake: Answering $1.05 (the pencil price) instead of the rubber. Correct approach: the question asks for the rubber, which is $0.05.
• Mistake: Overcomplicating with tax or discounts. Correct approach: simple two-variable algebra; the answer is $0.05.

Additional Notes

This problem is famous because the vast majority of people immediately answer $0.10, which feels like a natural split of the $1.10 total. But that answer makes the pencil $1.10 and the total $1.20, which contradicts the given numbers. The correct solution always requires writing the two equations and solving them. The game offers only two buttons, so once you rule out $0.10 by checking your arithmetic, $0.05 is the only possible choice. The pencil ends up costing $1.05, which is indeed exactly $1.00 more than the $0.05 rubber. The grammar "an rubber" is a deliberate minor typo and does not affect the math. The hint word "Rotate" is a nudge to turn the problem over in your head, not a motion control.