If the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up (+1).
If the number you are rounding is followed by 0, 1, 2, 3, or 4, round the number down (no change).
23.638 ≈ 23.64
74.827 ≈ 74.83
therefore:
23.638 + 74.827 ≈ 23.64 + 74.83 = 98.47 ⇒ answer C
