1460.21 – Target Products

For each case below, estimate which two numbers have a product that's closest to the target number. Then use your calculator to check. Keep going until you get closest to the target.

  1. 10, 11, 12, 13, 14, 15, target: 170
  2. 7, 10, 13, 16, 19, 22, target: 200
  3. 24, 30, 36, 19, 22, target: 715
  4. 13, 21, 29, 38, 46, 54, target: 1000
Solution

This will involve lots of guessing-and-trying, since there are 15 possible products for each case. One way to speed things up is to suggest that students try dividing a trial factor into the target number to see whether they get something that's close to another possible factor in the list. The best answers are these:

  1. 12×14=16812 \times 14 = 168
  2. 13×16=20813 \times 16 = 208
  3. 24×30=72024 \times 30 = 720
  4. 21×46=96621 \times 46 = 966