3.6.2 Try some yourself
Without using your calculator, find the following:
(a) 100.001 + 10.1
(b) 100.001 − 10.1
Suppose you went shopping with a friend and your combined bill came to £85. You knew that you had spent £47.65. What was your friend's share of the bill?
Your friend's share of the bill is £85 − £47.65 = £37.35. There are many ways to do this subtraction. Setting out as a formal sum is one approach, but counting on (as an assistant may do to give change) is another (from £47.65 a further 35 p is needed to make £48, then £2 to make £50 and £35 to make £85 gives £37.35).