Answer:
c. 1,000,000
Explanation:
Notice the measurements of the quarter is in millimetres, whereas the pile is given in kilometres. First, find the conversion from kilometres to millimetres.
2 km = ? mm
Usually, we know there are a thousands metres in a kilometre.
1 km = 1000 m
One meter has a hundred centimetres.
1 m = 100 cm
One centimeter is ten millimetres.
1 cm = 10 mm
Combine all of the measurements together.
1000*100*10 mm = 1 km
1,000,000 mm = 1 km
To get from millimetres to kilometres, multiply the kilometres by 1,000,000.
2 km = ? mm
(2 km)(1,000,000) = ? mm
2,000,000 mm = 2 km
We need 2,000,000 mm to make a 2 km pile. HOWEVER, we are using quarters, and each quarter is 2 mm thick. Divide the total milimetres by the thickness of a quarter.
2,000,000 mm ÷ 2 mm/quarter = 1,000,000 quarters
Therefore, you would need 1 million (1,000,000) quarters to make a 2 kilometre high pile.