4.4 Decimal problems

Now try the following activity.

Activity 33: Using decimals

An illustration showing items and their prices in pounds: A bottle of milk for 1.95, a box of corn flakes for 2.65, a receipt for 4 meals for 56.60.
Figure 25 Using decimals

Solve these problems involving decimal numbers without using a calculator.

  1. You buy a box of corn flakes for £2.65 and a bottle of milk for £1.98.
    1. What is the total cost of these items?
    2. You pay for them with a £5 note. How much change should you get?
  2. You go on holiday to Italy. The rate of exchange is £1 = €1.4. How many euros do you get for £8?
  3. You go out for a meal with three friends, and the total cost of the meal is £56.60. You decide to split the bill equally. How much does each of you pay?
  4. Convert 6.25 m to cm. (Remember that 100 cm = 1 m.)

Answer

  1. The answers are as follows:

    1. Add the cost of the two items:

      The sum £2.65 + £1.98 = £4.93.

      (Keep the decimal points in line.)

      The total cost of the items is £4.63.

    2. Take away the total cost from £5:

      The sum £5.00 – £4.63 = £0.37.

      You should get 37p change from £5. You may have used a different method to work this out.

  2. Multiply the exchange rate in euros (€1.4) by the amount in pounds (£8):

    The sum 1.4 × 8 = 11.2.

    So £8 = €11.20. You may have used a different method to work this out.

  3. Divide the total cost (£56.60) by the number of people (4):

    The sum 56.60 ÷ 4 = 14.15.

    You would each pay £14.15.

  4. To convert 6.25 m into cm, you need to multiply the amount by 100.

    • 6.25 × 100 = 625

    So the answer is 625 cm.

Summary

In this section you have learned about how:

  • the value of a digit depends on its position in a decimal number
  • to approximate answers to calculations involving decimal numbers
  • to add, subtract, multiply and divide using decimal numbers.

This will help when working with money and measurements.

OpenLearn - Everyday maths 1 (Northern Ireland)
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