A hot-air balloon is filled with air to a volume of 4.00 10 3 m 3

Question:

A hot-air balloon is filled with air to a volume of 4.00 × 10³ m³ at 745 torr and 21^oC. The air in the balloon is then heated to 62^oC, causing the balloon to expand to a volume of 4.20 × 10³ m³. What is the ratio of the number of moles of air in the heated balloon to the original number of moles of air in the balloon?