Question

21 is obtained by adding one-fifth of that number to one -half of that number.What is that number?

Answer 1

$Let \: a \: number \: be \: \pink {x}$

/*According to the problem given */

$One-fifth \:of \: the \: number = \frac{x}{5}$

$One-half\: of \: the \: number = \frac{x}{2}$

$Sum \: of \: \frac{x}{5} \:and \: \frac{x}{2} = 21$

$\implies \frac{x}{5} + \frac{x}{2} = 21$

$\implies \frac{2x + 5x}{10} = 21$

$\implies \frac{7x}{10} = 21$

$\implies x = 21 \times \frac{10}{7}$

$\implies x = 3 \times 10$

$\implies x = 30$

Therefore.,

$\red{ Required \: number } \green { = 30}$

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