Measurement Problems

Dr Martin the chemist is weighing out some medical pills. He has some 5g weights and some 7g weights. Can he weigh exactly 38g of medical pills?








Freddo has had a nice swim in the bottom of the well and decides that now is the time to get out. Freddo climbs 3m up the wall of the well and then rests. But the wall is slippery and he then slips down 1m. He is so tired he goes to sleep for the rest of the day. The next day he does the same thing. Climbs up 3m, slips back 1m, and goes to sleep. In fact he does this every day until he gets out of the well. Now the well is 13m deep.
How long does it take Freddo to climb out of the well?