62
Rounding up and rounding down
Textbook: Part 2, lesson 62, pp. 72–74
GoalRounding up and rounding down.
New words
rounding up · ortig‘i bilanrounding down · kami bilanbox · qutinumber needed · kerakli son
Explanation
Sometimes a number is rounded up or down regardless of the digit. Rounding down replaces the digits after the given place with 0: 4 321 ≈ 4 300 (rounded down to hundreds). Rounding up raises the place by 1: 4 321 ≈ 4 400 (rounded up). In life rounding up is needed so that there is no shortage: 53 books at 10 per box need 6 boxes.
Worked examples
4 321: rounded down 4 300, rounded up 4 400.
285 pupils, 40 seats per bus: 285 : 40 = 7 remainder 5, so 8 buses are needed.
Class activity
“How many boxes?”: count notebooks or pencils in class and find, rounding up, how many boxes of 10 are needed.
Practice
1
Round 4 321 down to the hundreds.
4 300
2
Round 4 321 up to the hundreds.
4 400
3
53 books are packed 10 per box. How many boxes are needed?
6
4
285 pupils go on a trip and each bus has 40 seats. How many buses are needed?
8