Solution: (1) Let the circular runway be x meters.
x =(3+4)×45
=7×45
=3 15
(2) Suppose Xiaomi and Tang Xiao meet again after one second, then
(4-3)x=3 15
x=3 15
Answer: (1) Circular runway 315m.
(2) If we go in the same direction, Xiaomi and Tang Xiao will meet again in 3 15 seconds.
Arithmetic thinking:
( 1)(3+4)×45 = 7×45 = 3 15(m)
(2) 315 ÷ (4-3) = 315 ÷1= 315 (seconds)
Answer: (1) Circular runway 315m.
(2) If we go in the same direction, Xiaomi and Tang Xiao will meet again in 3 15 seconds.