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Let’s Subtract Big Numbers
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Today we will be… Solving subtraction problems involving
money.
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Mental Oral Starter
What is the total of these coins?
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Mental Oral Starter
The total is 82p!
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Mental Oral Starter
What is the total of these coins?
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Mental Oral Starter
What is the total of these coins?
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Mental Oral Starter
What is the total of these coins?
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13p
I have this much money. I’m buying one teddy bear and want to know if I can afford one
more. Write the subtraction calculation you will use to help me work it out.
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13p
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Can you use partitioning to help me solve it?
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Begin by partitioning the numbers. Now cross out the number of tens and ones you are taking away. Will
you need to exchange a tens counter for ten ones?
10 1
10
1 10 1 1
1
10
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Yes! We need to exchange. One tens counter will become ten ones counters. Once we have crossed out 13’s worth of counters, what is left will be the answer.
10 1
10
110✘ 10 1 1
1✘ ✘✘
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1
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Did you get the answer 19? That means I can afford another teddy
bear!
10 1
10
110✘ 10 1 1
1✘ ✘✘ 1
1 1 1 1
1 1
1 1
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28p
How much money will I have after buying this cupcake?
What is the subtraction calculation you will be solving?
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Partition the numbers and cross out the tens and ones you’re taking away. Will you need to exchange for this
calculation?
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Did you reach the same answer? Well done! I would have 37p left after I
bought the cupcake.
1
10 1
10
110 10 1 1
1✘
1 1 1
1 1
1
1 1
1 11010
10 10✘✘
1
1
1
1 1
1 1
✘✘ ✘✘✘✘✘
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45p
I owe a friend £3.50. If I buy these trainers, will I still be able to pay them back?
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I’ll give you a tip: It’s best to work with the numbers in one unit. I suggest changing all the
amounts to pence before calculating. What will be the subtraction calculation you will be
solving this time?
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45p
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Partition the numbers and cross out the tens and ones you’re taking away. Will you need to exchange for this
calculation?
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If I bought the trainers I wouldn’t have enough to pay back £3.50 to my
friend. I need to save some more before I buy them.
10 1 1
1 1
110
10
10 110 10
100
10
10
10 1
1 1
1
100
100 ✘✘ ✘✘✘
✘ ✘✘✘
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Plenary
Jenny has 87p. She gives her brother Tom some money and has 76p left. She then gives her brother
Harry 28p. How much money does each person have in the end?
Jenny:
Tom:
Harry:
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Plenary Jenny has 87p. She gives her brother Tom some money and has 76p left. She then gives her brother
Harry 28p. How much money does each person have in the end?
Jenny:
Tom: 11p
Harry: 28p
87 - 76 =
10 110
10 10
10 10
10
10 1
1
1
1
1
1✘✘✘✘✘✘
✘✘✘✘
✘✘✘
Jenny gave Tom 11p.
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Plenary Jenny has 87p. She gives her brother Tom some money and has 76p left. She then gives her brother
Harry 28p. How much money does each person have in the end?
Jenny: 48p
Tom: 11p
Harry: 28p
76 - 28 =
10 110
10 10
10 10
10
1
1
1
1
1✘
Jenny had 48p left.
1 1
1 1
1 1
1 1
1 1
✘✘✘✘✘✘✘✘✘
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