Answer: D) 200 mm
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Work Shown:
1 meter = 100 cm
3 meters = 300 cm (multiply both sides by 3)
15 boxes are 300 cm tall combined, so 300/15 = 20 cm is the height of each box.
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Unfortunately 20 cm isn't listed as an answer choice, but we can convert to km and see what happens
20 cm * (1 m/100 cm)*(1 km/1000 m) = 20/(100*1000) = 0.0002 km
It's close, but off by a digit. Choice B has two zeros while 0.0002 has three zeros between the decimal point and the '2'.
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Let's convert to mm and see what happens
20 cm * (10 mm/1 cm) = 200 mm
Through trial and error, we arrived at the final answer.