2
Hundreds, tens and ones in pounds
Discover Mathematics P2: Term 2, Lessons 61–70
GoalBuild amounts with 100, 10 and 1 LE notes, and add them with regrouping.
New words
hundreds · 100 LE notestens · 10 LE notestrade · swap ten notes for one bigger note
Explanation
We can show any amount with 100 LE, 10 LE and 1 LE notes. Put them on a mat with three columns: hundreds, tens and ones. 243 LE is 2 hundred notes, 4 ten notes and 3 one notes. To add, add the ones first, then the tens, then the hundreds. If there are 10 or more one notes, trade ten 1 LE notes for one 10 LE note and move it to the tens column. In 27 + 37, the ones are 7 + 7 = 14. Trade ten ones for one ten, keep 4 ones, and add the tens: 2 + 3 + 1 = 6. The answer is 64.
| 100 LE notes | 10 LE notes | 1 LE notes |
|---|---|---|
| 2 | 4 | 3 |
Worked examples
Show 243 LE with notes: 2 hundreds, 4 tens and 3 ones. 200 + 40 + 3 = 243.
Add 135 LE and 242 LE. Ones: 5 + 2 = 7. Tens: 3 + 4 = 7. Hundreds: 1 + 2 = 3. The sum is 377 LE.
Add 126 LE and 38 LE. Ones: 6 + 8 = 14, so trade ten ones for one ten. Tens: 2 + 3 + 1 = 6. Hundreds: 1. The sum is 164 LE.
Class activity
Money mat game. Draw a mat with three columns on paper: hundreds, tens, ones. Use play money. Your partner calls an amount such as 307 LE and you build it on the mat. Then add one more amount and trade ten notes for one bigger note when you need to.
Practice
1
A mat has 3 hundred notes, 5 ten notes and 7 one notes. What is the amount?
| 100 LE notes | 10 LE notes | 1 LE notes |
|---|---|---|
| 3 | 5 | 7 |
357 LE.
2
Write 305 LE in hundreds, tens and ones.
3 hundreds, 0 tens and 5 ones.
3
Add 214 LE and 150 LE.
Ones 4 + 0 = 4, tens 1 + 5 = 6, hundreds 2 + 1 = 3. The sum is 364 LE.
4
Add 47 LE and 25 LE. Do you need to trade ten ones for a ten?
Yes. 7 + 5 = 12, so trade ten ones for one ten. Tens: 4 + 2 + 1 = 7. The sum is 72 LE.
5
Hamza has ten 10 LE notes. Which single note can he trade them for?
One 100 LE note, because ten tens make 100.