Question

a/2 + a/4 + a/8 =21​

Answer 1

Answer:

a=24

Step-by-step explanation:

$\frac{a}{2} + \frac{a}{4} + \frac{a}{8} = \frac{21}{1} \\ lcm \: of \: 2 \: and \: 4 \: and \: 8 \: is \: 8 \\ \frac{a(4) + a(2) + a(1)}{8} = \frac{21}{1} \\ \frac{4a + 2a + a}{8} = \frac{21}{1} \\ \frac{7a}{8} = \frac{21}{1} \\here \: i \: do \: cross \: multiplication \\ multiply \: the \: denominator \: of \: \frac{21}{1} \: is \: 1 \: with \: the \: numerator \: of \: \frac{7a}{8} \: is \: 7a \\ then \: multiply \: the \: numerator \: of \: \frac{21}{1} \: is \: 21 \: with \: the \: denominator \: of \: \frac{7a}{8} \: is \: 8 \: and \: equal \: those \\ 7a(1) = 21(8) \\ 7a = 168 \\ a = \frac{168}{7} \\ a = 24$

therefore, a=24