Sum of two digits of a 2-digit number must be less than (9 + 9) = 18sud21 wrote:How many 2-digit positive integers are there in which the sum of two digits is a 2-digit prime number?
Hence, the possible sums are 11, 13, and 17
Now 11, 13, and 17 can be written as the sum of two single digit in any of the following ways,
- # 11 = (2 + 9) = (3 + 8) = (4 + 7) = (5 + 6)
# 13 = (4 + 9) = (5 + 8) = (6 + 7)
# 17 = (8 + 9)
Hence, number of such 2-digit integers = 2*8 = 16
The correct answer is A.
