Answer:
The distance to the market is 2000 m
Step-by-step explanation:
∵ John runs to the market and comes back in 15 minutes
→ Change the min. to the sec. because the unit of his speed is m/s
∵ 1 minute = 60 seconds
∴ 15 minutes = 15 × 60 = 900 seconds
→ Assume that t1 is his time to the market and t2 is his time from
the market
∵ t1 + t2 = 15 minutes
∴ t1 + t2 = 900 ⇒ (1)
→ Assume that the distance to the market is d
∵ His speed on the way to the market is 5m/s
∵ Time = Distance ÷ Speed
∴ t1 = d ÷ 5 ⇒ (1 ÷ 5 = 0.2)
∴ t1 = 0.2d ⇒ (2)
∵ His speed on the way back is 4m/s
∴ t2 = d ÷ 4 ⇒ (1 ÷ 4 = 0.25)
∴ t2 = 0.25d ⇒ (3)
→ Substitute (2) and (3) in (1)
∵ 0.2d + 0.25d = 900
∴ 0.45d = 900
→ Divide both sides by 0.45
∴ d = 2000 m
∴ The distance to the market = 2000 m
