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Numbers, units and arithmetic
Numbers, units and arithmetic

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3.6.2 Try some yourself

Activity 36

Without using your calculator, find the following:

  • (a) 100.001 + 10.1

  • (b) 100.001 − 10.1


  • (a)

  • (b)

Activity 37

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).