Class 8 Playing With Numbers

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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