Challenge Level

100 = 50$\times$2$\times$1$\times$1 not all different

= 10$\times$5$\times$2$\times$1 good! Sum = 18

Is there another way?

Factors of 100 not used: 4, 20, 25

100 = 4$\times$25$\times$1$\times$1 not all different

= 4$\times$5$\times$5$\times$1 not all different. Cannot use 4

= 25$\times$2$\times$2$\times$1 not all different. Cannot use 25

100 = 20$\times$5$\times$1$\times$1 not all different. Cannot use 20

This problem is taken from the UKMT Mathematical Challenges.

You can find more short problems, arranged by curriculum topic, in our short problems collection.