Question

b decays, the number of a and b decays undergone is:

• A. 7 and 5
• B. 7 and 7
• C. 5 and 7
• D. 7 and 9

Answer 1

Answer: (B)

7 and 7

Answer 2

Let number of a decays are x and number of b decays are y. Then

92 – 2x + y = 85

Or 2x – y = 7 … (1)

And 238 – 4x = 210

\ x = 7

Substituting this value in Eq.(1), we get

y = 7