Pisa数学の試験を解いてみよう。Maths question of PISA
2013年 12月 11日
Helen's got a new bike. It has a speedometer which sits on the handlebar, which tells her the distance she travels and her average speed for the trip.
Helen rode her bike from home to the river, which is 4km away. It took her 9 minutes. She rode home using a shorter route of 3km. This only took her 6 minutes.
What was Helen's average speed in km per hour for the trip to the river and back?