D=RT word problem. Need help!!!please

[blaze042500]

I need help with this problem from singapore math.

Terry drove for 40minutes at an average speed of 90km/h. Then he drove for 20minutes to complete the remaining 23 km. Find his average speed for the whole trip.

 

[Deleted member 4993]

I need help with this problem from singapore math.

Terry drove for 40minutes at an average speed of 90km/h. Then he drove for 20minutes to complete the remaining 23 km. Find his average speed for the whole trip.

Terry drove for 40minutes at an average speed of 90km/h

How far did he drive at 90 km/h? = d₁

What is the total distance he drove = 23 + d₁

What is total time he drove = 20 + 40

Average speed = (total distance)/(total time)

 

[HallsofIvy]

Be careful of your units: the "40" and "20" are in minutes while the speeds are in "km per hour". 40 minutes is 2/3 of an hour and 40+ 20= 60 is one hour.