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Numbers, units and arithmetic
Numbers, units and arithmetic

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Activity 20

Place the following masses in order, with the lightest first:

  2125 mg   1.9 g   0.02 kg


To compare these masses, convert them all to the same units (it doesn’t matter which unit you choose, so long as all are converted to the same). Choosing grams gives 2.125 g, 1.9 g and 20 g. Placing these in order gives:

  1.9 g,    2.125 g,    20 g.

In the original units, this is

  1.9 g,    2125 mg,    0.02 kg.

Activity 21

Place each of the following sets of quantities in order, smallest first.

  • (a) X = 0.5 l   Y = 490 cl   Z = 510 ml

  • (b) X = 20p   Y = £0.02

  • (c) X = 0.039 kg   Y = 4 g   Z = 30 000 mg


  • (a) First convert to centilitres, say:

  X is 50 cl;  Y is 490 cl;  Z is 51 cl.

So the order is X, Z, Y.

  • (b) First convert to pence, say:

  X is 20p;  Y is 2p.

So the order is Y, X.

  • (c) First convert to grams, say:

  X is 39 g;  Y is 4 g;  Z is 30 g.

So the order is Y, Z, X.