In the study, 240 male and 160 plus another 100 female bats have been tagged, so that 500 bats have been tagged altogether. If x more male bats must be tagged for
3
5
of the total number of bats to be male, the proportion
male bats
total bats
=
240+x
500+x
=
3
5
must be true. Multiplying each side of
240+x
500+x
=
3
5
by 5(500+x) gives 5(240+x)=3(500+x) which simplifies to 1200+5x=1500+3x. Therefore,x=150,and 150 more male bats must be tagged; this will bring the total to 390 male bats out of 650 bats, which is equal to