51
Comparing three-digit numbers
Textbook: Part 2, lesson 49, pp. 18–19
GoalPut numbers in increasing and decreasing order; compare using place-value sums.
New words
increasing order · o‘sish tartibidecreasing order · kamayish tartibirow, list · qatororder · tartib
Explanation
In increasing order we write numbers from smallest to greatest; in decreasing order from greatest to smallest. Compare by the number of digits first, then place by place. If place-value sums are given, first write them as numbers: 400 + 50 + 7 = 457.
Worked examples
108, 56, 307 in increasing order: 56, 108, 307.
376, 392, 220 in decreasing order: 392, 376, 220.
Class activity
“Stand in order”: give five children cards with three-digit numbers. First they line up in increasing order, then in decreasing order.
Practice
1
Write in increasing order: 987, 108, 56, 908, 307.
56, 108, 307, 908, 987
2
Write in decreasing order: 376, 392, 459, 220, 735, 448.
735, 459, 448, 392, 376, 220
3
Compare: 400 + 50 + 7 and 400 + 70 + 5.
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4
Compare: 800 + 60 and 800 + 6.
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