The fraction is a lie!

Algebra Level 1

Solve for n n :

13 + n 18 + n = 4 5 \large \frac{13 + n}{18 + n} = \frac{4}{5}

This is part of the series: " It's easy, believe me! "


The answer is 7.

Thành Đạt Lê by Thành Đạt Lê , 17, Singapore

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3 solutions

13 + n 18 + n = 4 5 5 ( 13 + n ) = 4 ( 18 + n ) 65 + 5 n = 72 + 4 n n = 7 \frac { 13+n }{ 18+n } =\frac { 4 }{ 5 } \\ 5(13+n)=4(18+n)\\ 65+5n=72+4n\\ n=7

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Abha Vishwakarma
Sep 1, 2018

13 + n 18 + n \frac{13 + n}{18 + n} = 4 5 \frac{4}{5}

18 + n 13 + n \frac{18 + n}{13 + n} = 5 4 \frac{5}{4}

13 + 5 + n 13 + n \frac{13 + 5 + n}{13 +n} = 5 4 \frac{5}{4}

1 + 5 13 + n \frac{5}{13 + n} = 5 4 \frac{5}{4}

5 13 + n \frac{5}{13 + n} = 1 4 \frac{1}{4}

20 = 13 + n

n = 7

I did this because I don't know multiplication tables after 12. I am lazy I know.

0 Helpful 0 Interesting 0 Brilliant 0 Confused

13 + n 18 + n = 4 5 \dfrac{13+n}{18+n}=\dfrac{4}{5}

Cross-multiplying, we get

65 + 5 n = 72 + 4 n 65+5n=72+4n

Simplifying, we get

n = 7 \color{#69047E}\boxed{n=7}

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