Question

2 Nos are in the ratio of 4:5 the first no is
increased 20%. and second number is
is decreased by 20%
What will be the ratio of new number. ​

Answer 1

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Given:

The numbers are in the ratio of 4:5

First number 4 is increased by 20%

Second number 5 is decreased by 20%

To find:

The new ratio = ?

Method:

$\\ \\ 20\% \: of \: 4 \\ \\ = \dfrac{20}{100} \times 4 \\ \\ = 0.2 \times 4 \\ \\ = 0.8$

$as \: first \: number \: 4\: got \: increased \\by \: 20\% \: we \: have \: to \: add \: first \: \\ number \: 4 \: with \: 0.8 \\ \: \\ the \: new \: first \: number \: = 4 + 0.8 \\ \\ = 4.8$

$\\ 20\% \: of \: 5 \\ \\ = \dfrac{20}{100} \times 5 \\ \\ = 0.2 \times 5 \\ \\ = 1$

$\\ \\ as \: second \: number \: 5 \: is \: decrease \\ by \: 20\% \: we \: have \: to \: subtract \: with \\ 1 \\ \\ \: new \: second \: number = \: 5 - 1 \\ = 4$

Therefore, ratio of new numbers are

$\\ \\ \dfrac{4.8}{4} \\ \\ = \dfrac{1.2}{1} \\ \\ = \frac{12}{10} \\ \\ = \dfrac{6}{5}$

Required Answer:

Thus, the ratio of new numbers are 6:5

Additional points:

While solving, if a number is decrease by percentage, always subtract and if it is increased by percentage always do addition