Question

Find the third proportional to:
(i) $36$ and $18$
(ii) $5.25$ and $7$
(iii) Rs. $1.60$ and Rs. $0.40$

Answer 1

Find third proportional to

(i) 36 and 18

$So{l}^n$ The third proportional of two numbers

a and b is defined to be that number c

such that $a:b=b:c$

So, here we want to find a number c

such that

$36:18=18:c$

$\Rightarrow 36\times c=18\times 18$

$36c=324$

$c=\frac{324}{36}$

$c=9$

(ii) 5-25 and 7

$So{l}^n$

$5:25:7=7:c$

$5.25\times c=7\times 7$

$5.25c=49$

$c=\frac{49}{5.25}$

$c=9.33$

(ii) Rs 1.60 and Rs 0.40

$So{l}^n$

$1.60:0.40=0.40:c$

$1.60\times c=0.40\times 0.40$

$c=\frac{0.1600}{1.60}$

$c=0.1$