Question

if the third proportion to 7 and x is 28,find the value of x

Answer 1

then

x:7::28:x,

x/7 = 28/x,

x²=28×7,

x²=(2×2×7)×7,

then

x=2×7,

x=14

Answer 2

a:b::b:c
7:x::x:28
x×x=28×7
x²=196
x=14
So proportion=7:14::14:28