Length x width x height. Plug in the numbers, the bottom one, the length is 5, width is 3, height is 9. 5 x 3 = 15. 15 x 9 = 135. Now considering you still have the top one to do, we can eliminate A, B, and C as answer choices. But if you want proof to solve it, the top figure is length 8 x width 3 x height 3. 8 x 3 = 24. 24 x 3 = 72. 135 + 72 = 207. Recap:
Let the hall be A=1. For 3 hours 16 people can decorate the hall. Then P1=A\(t1.number people1) P=1/48. That is for 1 person. You have 24 people to decorate the same hall. Their P2 will be (1/48).24=1/2. t2=A/P2=2 hours
