Question

Find the value of a so that given four numbers are in proportion
a) 9,12,a,8
B)a,4,15,30
C)30,a,45,60
D)14,a,7,9

Answer 1

Step-by-step explanation:

given

1) 9:12:a:8

$\frac{9}{12} = \frac{a}{8} \\ \\ cross \: multiply \: this \\ \\ 9 \times 8 = 12 \times a \\ \\ 12a \: = 72 \\ \\ a = \frac{72}{12} \\ \\ a \: = 6$

$2) \frac{a}{4 } = \frac{15}{30 } \\ \\ \\ now \: c \:cross \: multiply \\ \\ a \times 30 = 15 \times 4 \\ \\ a = \frac{60}{30} \\ a = 2$