Two and Two
Why do this problem?
This problem offers an opportunity to practise addition in a more interesting and challenging context than is usual. It requires students to work systematically, record their progress efficiently and apply their understanding of place value.
Possible approach
This printable worksheet may be useful: Two and Two
Write the following sum on the board and ask students to complete it.
| 8 | 6 | 1 | ||
| + | ? | ? | ? | |
| 1 | 4 | 2 | 7 |
Expect justifications for any suggestions.
| b | b | |
| + | c | b |
| a | c | c |
"How can we approach this?"
To finish off, students could present their approach to the rest of the class, with emphasis on explaining clearly why they are convinced that they have found all the possible solutions.
Key questions
What must "F" be?
What does that tell you about "T"?
Are you certain you have considered all the possibilities?
Possible support
Suggest students start with Spell by Numbers
Possible extension
Suggest students find other word sums that work.
Here are some possibilities that they might consider:
ONE + TWO = THREE
ONE + THREE = FOUR
Why are some impossible?
Can they make a word subtraction?
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