Question

what number should be added to 1,2,5 and 7 so as to form four numbers in proportion

Answer 1

LET X BE ADDED TO ALL

So, 3+x,5+x,13+x,19+x these now are in proportion.

using proportion formula

3+x/5+x=13+x,19+x

=(3+x) (19+x)=(13+x)(5+x)

=57+3x+19x+x^2=65+13x+5x+x^2

=22x+57=18x+65

=22x-18x

=4x=8

x=2