Question

in a library there are 990 books. if the number of english books is 4 times the number of mathematics book and the number of mathematics books is twice the number of science books . find the numbrr ofboks of each subject. please tell the solution fast and step by step and correct answer​

Answer 1

$\huge\sf\pink{Answer}$

☞ Number of English books = 720

☞ Number of Maths books = 180

☞ Number of Science book = 90

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$\huge\sf\blue{Given}$

✭ Total books in a library = 990

✭ Number of English books is 4 times the number of Maths book

✭ Number of Maths book is twice the number of Science book

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$\huge\sf\gray{To \:Find}$

☆ Number of each book?

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$\huge\sf\purple{Steps}$

$\sf\underline{As \ per \ the \ Question}$

Let

◕ Number of English books be E

◕ Number of Maths book be M

◕ Number of Science book be S

So now,

➢ $\sf E = 4M \qquad\frac{\quad}{}eq(1)$

➢ $\sf M = 2S \qquad\frac{\quad}{}eq(2)$

$\sf \dashrightarrow E = 4×2S = 8S$

$\sf\dashrightarrow S + 2S + 8S = 990$

$\sf\dashrightarrow 11S = 990$

$\sf\dashrightarrow S = \frac{990}{11}$

$\sf\color{lime}{\dashrightarrow S = 90}$

Substituting the values in eq(2),

$\sf\leadsto M = 2S$

$\sf\leadsto M = 2×90$

$\sf\color{aqua}{\leadsto M = 180}$

Substituting the values in eq (1),

$\sf\longmapsto E = 4M$

$\sf\longmapsto E = 4×180$

$\sf\color{red}{\longmapsto E = 720}$

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Answer 2

Let ,

The number of english books be " e "

The number of maths books be " m "

The number of science books " s "

Given ,

The number of english books is 4 times the number of mathematics book

e = 4m --- (i)

The number of mathematics books is twice the number of science books

m = 2s --- (ii)

And the total number of books in school is 900

Thus ,

e + m + s = 990

4m + 2s + s = 990

4(2s) + 3s = 990 { since, m = 2s }

8s + 3s = 990

11s = 990

s = 990/11

s = 90

Put the value of s = 90 in eq (ii) , we get

m = 2 × 90

m = 180

Put the value of m = 180 in eq (i) , we get

e = 4 × 180

e = 720

. ° . The number of english , maths and science books are 720 , 180 and 90