Question

The cost of $\frac{3}{4}litre$ of milk is $21Rs$ . The cost of $1$ $litre$ of milk is.

• A. $21Rs$
• B. $28Rs$
• C. $\frac{63}{4}Rs$
• D. $84Rs$

Answer 1

The correct option is B

$28Rs$

Given: the cost of $\frac{3}{4}litre$ of milk $\frac{3}{4}$$=$ $21Rs$.

The cost of $1$ $litre$ of milk $=$ $21$ $÷$ $\frac{3}{4}$

For the above calculation, find the reciprocal of $\frac{3}{4}$.

Reciprocal of $\frac{3}{4}$ $=$ $\frac{4}{3}$.

Then, multiply the reciprocal of $\frac{3}{4}$ with $21$.

$\frac{21}{1}\times \frac{4}{3}$ $=$ $\frac{(21\times 4)}{(1\times 3)}$

$=\frac{84}{3}$

reduce the fraction $\frac{84}{3}$ into its lowest terms.

$\frac{84÷3}{3÷3}$ $=\frac{28}{1}$

So, we can say that the cost of $1$ $litre$ of milk $=$ $28Rs$.

Hence, option B is correct.