In this section we consider how to make the best use of calculators. We focus on the use of *brackets*. We will then look at the use of the *memory* functions. Calculators vary a great deal both in the number of memories available and in how they are used. It is essential for you to learn how *your* calculator memory works.

Calculate , giving your answer to 3 decimal places.

Use the following keys to obtain the correct answer:

(
4
.
7
+
3
.
2
)
÷

(
8
.
6
–
3
.
1
)
=

You should obtain 1.436363636, which rounds to 1.436 to 3 decimal places.

Note how brackets have been used around both the numerator and the denominator of the fraction.

Zarah uses her calculator to obtain an answer to,

She obtains the answer –3.75 to 2 decimal places.

(a)

Use estimation to show that her answer is incorrect.

≈ ≈ = 0.05

The estimate indicates that Zarah's negative answer must be incorrect.

(b)

Describe the error she made when using her calculator, and write down the calculation that she actually carried out.

Zarah forgot to include brackets around the denominator of the fraction. She actually calculated

– 3.8

(c)

Calculate the correct answer, correct to 3 significant figures.

The correct answer can be obtained by using the following sequence of keys:

4 . 7 ÷ ( 1 0 2 – 3 . 8 ) =This gives a value of 0.047861507, which is 0.0479 to 3 significant figures.

Note that this compares well with the estimate.