Write two triangular numbers which add up to 49.

21+28=49

Step-by-step explanation:

Not much explanation.

The triangular numbers are the sums of the natural numbers.

T₁ = 1

T₂ = 1 + 2 = 3

T₃ = 1 + 2 + 3 = 6

T₄ = T₃ + 4 = 10

T₅ = T₄ + 5 = 15

T₆ = T₅ + 6 = 21

T₇ = 28

T₈ = 36

T₉ = 45

T₁₀ = 55

Let's subtract each from 49 and see if the result is on the list:

49-1=48, nope

49-3=46, 49-6=43, then 39, 34, 49-21=28, winner

The rest won't give any new possibilities.

Answer: 21 and 28