Mathematics
Grade-4-
Easy
Question
Use estimation and rounding to choose the appropriate answer for each problem:
In the morning, about 452 planes are taking off from the airport and 127 of the planes are delayed for more than 15 minutes. About planes take off within 15 minutes of the scheduled time.
- 450
- 130
- 320
- 127
Hint:
Rounding
One very simple form of estimation is rounding. Rounding is often the key skill you need to quickly estimate a number. This is where you make a long number simpler by ‘rounding’, or expressing in terms of the nearest unit, ten, hundred, tenth, or a certain number of decimal places.
For example, 1,654 to the nearest thousand is 2,000. To the nearest 100 it is 1,700. To the nearest ten it is 1,650.
The correct answer is: 320
Total planes scheduled to take off from the airport in the morning = 452 
450 (rounding off to nearest hundreds)
Total planes delayed for more than 15 minutes = 127 130 (rounding off to nearest hundreds)
Estimated total planes take off within 15 minutes after rounding to its nearest tens place= 450 – 130 = 320.
Thus, About 320 planes take off within 15 minutes of the scheduled time.
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