One day when Taro left home toward the school, 7 minutes after his leaving his mother noticed the thing left behind of Taro.
Although she pursued at the speed of 80 m/m immediately, she thought that she could not catch up Taro.
Then she borrowed a bicycle at the house of Taro's friend which is on the way and kept pursuing.
Although she took 3 minutes to borrow, she caught up with Taro just in front of the school gate.
The way from the house to a school is straight and the distance is 1500 m.
The graph below expresses the relation between the time after Taro leaves home and the distance of two persons.
Answer the following questions.
Noted that the speed which Taro walks, the speed which his mother walks, and the speed of the bicycle are constant respectively.
(1) Find the speed which Taro walks at the speed per minute.
(2) Find the distance from the house of Taro to his friend's house.
(3) Find the speed of the bicycle at the speed per minute.
Answer
(1) 75 m/m
(2) 480 m
(3) 255 m/m
Solution
(1) 1500 / 20 = 75 m/m
(2) 75 × 7 = 525
525 - 495 = 30 m
30 / (80-75) = 6 minutes
80 × 6 = 480 m
(3) (495 + 75 3) / ( X - 75) = 4 minutes
X = 180
180 + 75 = 255 m/m
