Near Doubles

I am learning to solve addition problems where the two numbers are easily related to doubles.

e.g. 9 + 9 = 18

Or

80 + 80 = 160

Craig has $79 and saves another $81. How much money does he have? 79 + 81 = ?

Step 1: Let’s use some notes and coins to represent this question.

$10$10$10$10$10$10$10

1

1

1

1

1

1

1

1

1

$10$10$10$10$10$10$10

1

$10

Step 2: If we move $1 from the $79 to the $80 then both piles will have $80.

1$10

Step 3: Swap the ten $1 coins for a $10 note and then both groups have $80

80 + 80 = 160

Kim drove 78km on Monday and 79km on Tuesday. How many kilometres has she driven? 78 + 79 = ?

Step 1: Let’s use our doubles to help us answer this question. Change the question into 80 + 80. This will be much easier to answer.

78 + 79 = ……

80 + 80 = 160

+2 +1

Step 2: We added 2 to the 78 and 1 to the 79 (a total of 3). So now we must subtract 3 from our answer of 160.

160 – 3 = 157

Now try these questions on your own.

Need some more practise? Try Pg55 of Teacher Tools Addition and Subtraction Book Numeracy resources

1) 69 + 71 = ?

2) 38 + 38 = ?

3) 89 + 92 = ?

4) 148 + 252 = ?

5) 119 + 119 = ?

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

140

76

181

400

238