Problems like 37 + … = 79

I am learning to add mentally the ones and tens separately when appropriate.

84

Tens Ones

Sam has $36 and is saving to buy a scooter for $78. How much more must he save?

Step 1: Let’s record what he needs.

Step 3: You can now see how much he must save.

$70 (seven $10) $8 (eight $1)

Step 2: Now record how much he actually has. $30 (three $10)

$6 (six $1)

Four $10 notes or $40 and two $1 coins or $2

$40 + $2 = $42 Sam must save $42

Important: Notice how both the ones and tens amount Sam has are both less than the amount he needs. This strategy works for problems like this.

Kate has $14 and is saving to buy a concert ticket for $48. How much must she save?

Step 1: Let’s record what she needs.

Step 3: You can now see how much she must save.

$40 (four $10) $8 (eight $1)

Step 2: Now record how much she actually has.$10 (one $10)

$4 (four $1)

Three $10 notes or $30 and four $1 coins or $4

$30 + $4 = $34. Kate must save $34

Important: Notice how both the ones and tens amount Kate has are both less than the amount she needs. This strategy works for problems like this.

Taine has $35 and is saving to buy a new watch for $89. How much must he save?

Step1: How many $1 coins must he save.

Step 2: How many $10 notes must he save.

4 ($4)

Step 3: Add the two amounts together. How much must he save?

5 ($50)

$50 + $4 = $54

Try doing this example in your head.

Now try these questions on your own.

Remember to add the ones and tens separately.

Need some more practise? Try Pg48 of Teacher Tools Addition and Subtraction Book Numeracy resources

1) 34 + …. = 76

2) 18 + …. = 59

3) 63 + … = 88

4) 12 + …. = 65

5) 36 + …. =87

Click again when you have completed each question and the answer will be displayed.

40 + 2 = 42

50 + 1 = 51

40 + 1 = 41

20 + 5 = 25

50 + 3 = 53