Chapter 16: Playing With Numbers
Ex 16.1
Find the values of the letters in each of the following and give reasons for the steps involved.
First 4 sums
5 and 6th sum
7 and 8th sum
9 and 10th sum
1. 3 A 2. 4 A 3. 1 A 4. A B 5. A B 6. A B
2 5 9 8 ✖ A 3 7 ✖ 3 ✖ 5
7. A B 8. A 1 9. 2 A B 10. 1 2 A
✖ 6 1 B A B 1 6 A B
Ex 16.1 Free PDF Download
Ex 16.2
1. If 21y5 is a multiple of 9, where y is a digit, what is the value of y?
2. If 31z5 is a multiple of 9, where z is a digit, what is the value of z? You will find that there are two answers for the last problem. Why is this so?
3. If 24x is a multiple of 3, where x is a digit, what is the value of x? (Since 24x is a multiple of 3, its sum of digits 6 + x is a multiple of 3; so 6 + x is one of these numbers: 0, 3, 6, 9, 12, 15, 18, …. But since x is a digit, it can only be that 6 + x = 6 or 9 or 12 or 15. Therefore, x = 0 or 3 or 6 or 9. Thus, x can have any of four different values.)
4. If 31z5 is a multiple of 3, where z is a digit, what might be the values of z?
Ex 16.2 Free PDF Download
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