Page 169 - NUMINO Challenge_M2

Answer
Key

Problem solving

1 The numbers in 3-digit addition that can be , are 7, 8, and 9.

If =7, 2 4

59
777

So, =3, =8. The sum of the tens place would be 8+9=17, which would
make the sum of the hundreds place 1+2+5=8, which does not work.
This proves that cannot be 7.

If =8, 2 4

59
888

So, =4, =9. The sum of the tens place would be 9+9=18, and the sum
of the hundreds place would be 1+2+5=8, which works.
Therefore, is 8.

If =9, 2 4

59
999

So, =5, =0. The sum of the tens place would be 0+9=9, and the sum of
the hundreds place would be 2+5=7, which does not work.
This proves that cannot be 9.

=8, =9, =4

2 Write the problem as an addition expression.

4 14
8
8 Write as addition
expression 4
14

The sum of the ones digits in the addition expression is 4+8=12.
=2

Type Study The sum of the ones digits cannot be 19 so the sum of and is 9.
There is no regrouping in the ones place, so the sum and is 14.
The sum of all the numbers, ( + + + ), is 14+9=23.

32 NUMINO Challenge M2