Using a Calculator Flashcards

All 8 cards in this deck

What are the steps to evaluate a calculation with a root over a fraction on a calculator in one go?
e.g. $\sqrt{\dfrac{9+7}{2.5}}$

1. Press the root key first, then the fraction key inside it, so the whole fraction is under the root.
2. Type the numerator and denominator with brackets where needed: $(9+7)$ and $2.5$ (fraction $=6.4$).
3. Write down all the figures on the display: $2.529822128$

How do you round a calculator answer to 3 significant figures?
e.g. display shows $4.643069317$

Count 3 figures from the first non-zero digit, then round using the next digit: $4.64$

What does the $x^{-1}$ key on a calculator give?

The reciprocal of the number, i.e. $1$ divided by it.
e.g. $8^{-1}=0.125$

What must you check on your calculator before evaluating an expression containing $\sin$, $\cos$ or $\tan$ of an angle in degrees?
e.g. $4\sin 23^\circ$

That it is in degree mode (D or DEG on the display).
Then $4\sin 23^\circ = 1.56$ to 3 s.f.

A calculator display reads $2.7\times10^{-3}$. What is this as an ordinary number?

$0.0027$

True or false? A calculator cannot make a mistake, so there is no need to check its answer against an estimate.

False. The calculator only does what you type, so an estimate checks that the calculation was entered correctly.

What are the steps to write a calculator display shown in standard form as an ordinary number?

e.g. display shows $2.4\times10^{5}$

1. Read the power: $5$
2. Positive power: move the decimal point that many places right (negative power: move left): $2.4 \to 240000$
3. Fill any gaps with zeros: $240\,000$

True or false? A calculator display showing $6\times10^{-4}$ means the answer is a negative number.

False. The negative power means a small positive number, $0.0006$.