Numbers, units and arithmetic
Numbers, units and arithmetic

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Numbers, units and arithmetic

3.8.1 Try some yourself

Activity 40

Without using your calculator, find the following.

  • (a) 75.6 ÷ 0.6

  • (b) 75.6 × 0.6

  • (c) 100.001 + 75.6 ÷ 0.6

  • (d) (100.001 + 10.1) × 60

Answer

  • (a)

  • (b) 75.6 × 0.6 = 75.6 × = 7.56 × 6 = 45.36.

  • (c) Carrying out the division first, use the result of part (a) to give:

  • 100.001 + 75.6 ÷ 0.6 = 100.001 + 126

  •  = 226.001.

  • (d) Carry out the addition in brackets first:

  • (100.001 + 10.1) × 60 = 110.101 × 60 = 1101.01 × 6 = 6606.06.

Activity 41

Try dividing 10 by 3, first without using your calculator, and giving your answer as a decimal. What is the difficulty? What answer does the calculator give?

Answer

10 ÷ 3 gives

   and so on.

Each time you divide by 3 you get a remainder 1, which gives 10 in the next column, so the decimal carries on forever. This is called a recurring decimal, because the 3 recurs repeatedly.

A scientific calculator gives 3.333333333 (it rounds to 10 digits).

Activity 42

Is the following statement true or false?

Multiplying one number by a second number always gives an answer greater than the first number.

Answer

False. For example, multiplying 7.9 × 0.8 in Question 1(a) gave 6.32, which is less than 7.9. In general multiplying a positive number by a number less than one gives a smaller number.

MU120_4M1

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