near doubles
Post on 06-Jan-2016
34 Views
Preview:
DESCRIPTION
TRANSCRIPT
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
top related