53
Adding three-digit numbers
Textbook: Part 2, lesson 51, pp. 22–23
GoalAdd three-digit numbers with regrouping.
New words
regrouping (carrying) · o‘tkazish10 ones · 10 birliksum · yig‘indichecking · tekshirish
Explanation
Ten of any place make one of the next place: 10 ones = 1 ten, 10 tens = 1 hundred. 358 + 173: 8 + 3 = 11 ones – 1 ten moves over, 1 one stays; 5 + 7 + 1 = 13 tens – 1 hundred moves over, 3 tens stay; 3 + 1 + 1 = 5 hundreds. The answer is 531.
Worked examples
279 + 385: 9 + 5 = 14, 7 + 8 + 1 = 16, 2 + 3 + 1 = 6. The answer is 664.
543 + 357 = 900: 3 + 7 = 10 ones, 4 + 5 + 1 = 10 tens, 5 + 3 + 1 = 9 hundreds.
Class activity
“Ten? Trade it!”: give children ones-cubes and tens-sticks. When a sum is given, they count the cubes and trade every 10 cubes for a stick.
Practice
1
358 + 173 = ?
531
2
483 + 468 = ?
951
3
279 + 385 = ?
664
4
At the market one seller sold 247 balloons and another sold 176. How many balloons in total?
423