40+30 = 70 (seconds), then three people should wait (40+30) × 3 = 2 10 (seconds) = 3.5 minutes.

Second, but this quotient is at most 17 and at least 6.

So the minimum value of this three-digit number is18× 6+6 =14, and the maximum value is18×17+17 = 323.

Can 3.26 be a multiple of 5 after subtracting a multiple of 3? So there are two answers:

(1) 1 cart and 7 carts; (2) 4 carts and 2 carts.

Four. 1170÷15 = 78 (m)

( 1) 1975÷( 1 170÷ 15)- 15

≈ 25- 15 = 10 (minutes)

(2) 1975- 1 170 = 805(m)

805÷78≈ 10 (minutes)

It takes him 10 minutes to get from home to the museum than to go to school.