# 2.8.1 Try some yourself

## Activity 9

What do the following mean?

(a) (5 + 8)/(4 − 2)

(b) 5 + 8/4 − 2

(c) (4 + 5)(5 − 2)

(d)

(e)

(f)

(g) (12 − 9)

^{−1}

### Answer

(a) Add 5 and 8, and then divide the result by the difference between 4 and 2. (This gives .)

(b) Add 5 to the division 8/4, and then subtract 2. (This gives 5.)

(c) Multiply the sum of 4 and 5 by the difference between 5 and 2. (This gives 27.)

(d) Multiply 9 by the square root of 4. (This gives 18.)

(e) Multiply 5 by 6, and then divide by 2. (This gives 15.)

(f) The cube of the square root of 25. (That is, 125.)

(g) The reciprocal of 12 minus 9. (That is, )

## Activity 10

What do these symbols mean?

(a) =

(b) <

(c) >

(d)

### Answer

(a) = means ‘equals’

*or*‘equal to’*or*‘which equals’.(b) < means ‘less than’

*or*‘which is less than’.(c) > means ‘greater than’

*or*‘which is greater than’.(d) means ‘is approximately equal to’.

## Activity 11

What do the following mean?

(a) mass ≥ 10 kg

(b) time < 2.4 × 10

^{6}h(c) 2/3 ≠ 0.67

### Answer

(a) The mass is greater than or equal to 10 kg.

(b) The time is less than 2.4 million hours.

(c) Two-thirds (or 2 divided by 3) is not equal to 0.67.