Question

The diameter of a wheel of a lorry is 150cm. If the lorry travels 376.8m, how many times does the wheel rotate?

Answer 1

Answer:  79 full rotations

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Explanation:

150 cm = 150/100 = 1.5 m

The wheel has a diameter of 1.5 meters

The circumference of the wheel is

C = pi*d

C = pi*1.5

C = 1.5pi

C = 4.71238898038469

I'm using my calculator's stored version of pi to get the most accuracy.

Then we divide the 376.8 over the circumference found

(376.8)/(4.71238898038469) = 79.9594434093682

Despite being very close to 80, we must round down to 79 because we don't have enough to get that full 80th rotation. In other words, we have 79 full rotations and then some change leftover.

Though for the sake of simplicity, I can see how it's useful to say "about 80 rotations" if 79 seems a bit clunky. I'll stick with 79 however. Let me know if your teacher instructs otherwise.