Question

The number of novels and science books in a
library are 45 and 20, respectively. The ratio
between the numbers of novels and history books
is equal to the ratio between the numbers of
history books and science books. Find the number
of history books in the library.​

Answer 1

ans - If x is the number of History books ..

Then,

45/x = x/20

= x*x = 45x20

=x*x = 900

= x*x = 30x30

therefore,

x=30

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