Question

Starting at home, Jessica traveled uphill to the grocery store for 18 minutes at just 20 mph. She then traveled back home along the same path downhill at a speed of 60 mph. What is her average speed for the entire trip from home to the grocery store and back?

It takes 45 minutes for 4 people to paint 5 walls. How many minutes does it take 6 people to paint 4 walls?

It takes 52 minutes for 5 people to paint 5 walls. How many minutes does it take 20 people to paint 20 walls?

It takes 48 minutes for 7 people to paint 7 walls.How many minutes does it take 20 people to paint 20 walls?

Answer 1

Try this solution with short explanation; note, the suggested way is not the shortest one; the answers are marked with red colour.

Task no. 2: another solution is 45* (4/5) / (6/4) = 24 min.