To correctly evaluate this we have to give algebraic values to both the width and the length, so the width would be X, and the legnth is 12 inches larger than the length so this would be expressed by: x+12, so the equation of the perimeter would be:
Now you just evaluate the equation for perimeter=144.
Pupils that chose Band: 60% Pupils that chose Chorus: 40% Boys in band: 70% Boys in chorus: 30% Probability of choosing boy = Probability of boy in band + Probability of boy in chorus P = 0.6 x 0.7 + 0.4 x 0.3 P = 0.54 The answer is D.