Question

Determine if the following is in proportion.

$15,45,40,120$

Answer 1

If $a,b,c,d$are in proportion then,

$a\times d=b\times c$

So, here we have $15,45,40,120$

in which

$a=15,b=45,c=40,d=120$

now, $15\times 120=1800$

and, $45\times 40=1800$

Hence $a\times d=b\times c$

So, $15,45,40,120$ are in proportion.