Maths Mate Sheet 7 Question 23 (Term 4 2014)
Prediction: I predict this question will be about addition because of the repeated pluses in the question.
Read: The digit sum for 95 is 9 + 5, or 14. How many two digit numbers have the digit sum of 9.
Clarification: None needed.
The Big Question: How many two digit numbers have the digit sum of 9.
Mathematician’s Toolbox: Have I seen a similar problem?
Solving: Firstly I know that all the nine times tables with two digit numbers add up to nine so I did: 2×9,3×9,4×9,5×9,6×9,7×9,8×9, 9×9 and 10×9. Thats 9 sums so the answer is 9.
Conclusion: So the answer was 9.