Question

224.
A number, on subtracting 15 from it, reduces to its 80%. What is 40% of that number?
45​

Answer 1

30

x-15=80x

------

100

x-15-4x

----

5

5x-75=4x

x=75

REQUIRED ANSWER

40

75×------=30

100

Answer 2

QuestioN :-

• A number, on subtracting 15 from it, reduces to its 80%. What is 40% of that number?

AnsweR :-

• 30 is the answer.

SolutioN :-

Let the number is 'x'

According to the Question ,

$\sf \: x - 15 = 80\% \: of \: x \\ \\ \sf \: x - 15 = { \frac{80 x}{100} } \\ \\ \sf \: x - 15 = \frac{4x}{5} \\ \\ \sf \: 5(x - 15) = 4x \\ \\ \sf \: 5x - 75 = 4x \\ \\ \sf \: 5x - 4x = 75 \\ \\ </strong><strong>\</strong><strong>b</strong><strong>o</strong><strong>x</strong><strong>e</strong><strong>d</strong><strong>{</strong><strong>\</strong><strong>r</strong><strong>e</strong><strong>d</strong><strong>{</strong><strong> \sf \: x = 75</strong><strong>}</strong><strong>}</strong><strong>$

The number is 75.

$\sf \: 40\% \: of \: 75 = \frac{75 \times 40}{100} \\ \\ = 75 \times \frac{4}{10} \\ \\</strong><strong> </strong><strong>\</strong><strong>b</strong><strong>o</strong><strong>x</strong><strong>e</strong><strong>d</strong><strong>{</strong><strong>\</strong><strong>b</strong><strong>l</strong><strong>u</strong><strong>e</strong><strong>{</strong><strong> = 30</strong><strong>}</strong><strong>}</strong><strong>$