Question

Two numbers are chosen from 1, 3, 5, 7, 147, 149 and 151 and multiplied together in all possible ways. The number of ways which will give us the product a multiple of 5,

Answer 1

1 and 5

3 and 5

7 and 5

151 and 5

5 and 5

147 and 5

149. and 5

Answer 2

Hence total number of ways are = 15 × 76 = 1140 [Ways]

Step-by-step explanation:

Multiples of 5 are 5,15,25,...,145  and so on.

• a = 5
• d = 10
• n = ?
• a  (n ) = 145

Here;

145 = 5 + [n − 1] 10

⇒ n = 15

Now choose one from these 15 numbers  and another one from any number which are  

151 + 1  / 2 = 76

Hence total number of ways are = 15 × 76 = 1140 [Ways]