100
20 of them
3 pairs of whole numbers add up to 7: 1 +6, 2+5, 3+4 (0+7 also equals 7, but zero is not a whole number)
6
49 of them.
100
20 of them
An infinite number.
3 pairs of whole numbers add up to 7: 1 +6, 2+5, 3+4 (0+7 also equals 7, but zero is not a whole number)
6
49 of them.
There 4 pairs of primes that can give a sum 40 in addition. They are (3,37), (11,29), (17,23),(19,21).
100
Only one pair.
Just 3 + 3
number of pairs of odd numbers whose sum is 32: 8pairs of odd numbers whose sum is 32:1, 313, 295, 277, 259, 2311, 2113, 1915, 17
The sum of two numbers is a whole number if both of the numbers are whole numbers, or if the sum of two fractions can be simplified to a whole number.