Let's assume that the number of boys and girls who join the club is x.
After x boys and x girls join the club, the number of boys and girls in the club will be:
Boys: 3 + x
Girls: 5 + x
According to the problem, the ratio of boys to girls after x boys and x girls join the club is 3:4.
Therefore, we can write:
(3 + x) / (5 + x) = 3/4
Multiplying both sides by (5 + x) gives:
3 + x = (3/4) * (5 + x)
Multiplying both sides by 4 gives:
12 + 4x = 15 + 3x
Subtracting 3x from both sides gives:
9 = x
Therefore, the number of boys and girls who join the club is 9.
The total strength of the club will be:
3 (original boys) + 5 (original girls) + 9 (new boys) + 9 (new girls) = 26
Therefore, the total strength of the club will be 26.