### Brain Teasers

# Math and Money

In order to encourage his son to study math, a father agrees to pay his boy 8 cents for every problem correctly solved and to fine him 5 cents for each incorrect solution. At the end of 26 problems, neither owes anything to the other.

How many problems did the boy solve correctly?

How many problems did the boy solve correctly?

### Answer

Ten Problemslet x represent the number of problems answered correctly, then 26-x represent the number of problems answered incorrectly:

8x - 5(26-x) = 0

8x - 130+5x = 0

13x = 130

x = 10

26-x = 16

Therefore, 10 answers were correct and 16 were incorrect.

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## Comments

That was in my math book!

freaky

way too easy

It's even easier than the given solution. This was about five seconds in my head.

The ratio he earns is 8::5. 8+5=13. 26/13=2. 2*5=10.

I take it back, it was probably less than five seconds.

The ratio he earns is 8::5. 8+5=13. 26/13=2. 2*5=10.

I take it back, it was probably less than five seconds.

Assume he got them all correct - that's 8 x 26 cents. For every one wrong he loses 13 cents and he lost the lot so thats 8 x 26 / 13 = 16 wrong or 10 right!

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