Question

Find the value of $x$ in the following proportions:

$\left(i\right)7:15::x:30$

$\left(ii\right)x:3::12:18$

$\left(iii\right)30:x::45:24$

$\left(iv\right)8:16::25:x$

Answer 1

If $a:b::c:d$ then $a\times d=b\times c$

$\left(i\right).7:15::x:30$

$\Rightarrow 7\times 30=15\times x$

$\Rightarrow \frac{7\times 30}{15}=x$

$\Rightarrow 7\times 2=x$

$\Rightarrow x=14$

$\left(ii\right).x:3::12:18$

$\Rightarrow x\times 18=3\times 12$

$\Rightarrow x=\frac{12\times 3}{18}$

$\Rightarrow x=2$

$\left(iii\right).30:x::45:24$

$\Rightarrow 30\times 24=x\times 45$

$\Rightarrow \frac{30\times 24}{45}=x$

$\Rightarrow \frac{2\times 24}{3}=x$

$\Rightarrow 16=x$

$\left(iv\right).8:16::25:x$

$\Rightarrow x\times 8=16\times 25$

$\Rightarrow x=\frac{25\times 16}{8}$

$\Rightarrow x=25\times 2$

$\Rightarrow x=50$