Unit 1 - Rounding numbers to Significant Figures

Sometimes we just need a rough or round answer to a question. When we are faced with a long number, we could round it off to the nearest hundred, or nearest thousand. And when we get a long decimal answer, we could round it off to a certain number of decimal places.

Another method of giving an approximated answer is to round off using significant figures.

The word significant means important. The closer a digit is to the beginning of a number, the more significant it is.

Example 1:

With the number 4657, the 4 is the most significant digit, because it tells us that the number is 4  thousand and something. It follows that the 6 is the next most significant, and so on.

Example 2:

With the number 0.0000076253, the 7 is the most significant digit, because it tells us that the number is 7 millionths and something. The 6 is the next most significant, and so on.

We round off a number using a certain number of significant figures. The most common are 1, 2 or 3 significant figures.

Remember the rules for rounding up:

If the next number is 5 or more, you round up.

If the next number is 4 or less, you do not round up.

Question 1:

Round £43884 to 2 sig. figs. (significant figures).

Question 2:

What is 0.023478 to 3 sig. figs.?

Question 3: 

Round 3333 to 2 sig. figs.

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Answers:

1.) £44000

2.) 0.0235

3.) 3300

Unit 2 - Volume of Triangular Prism

Triangular Prism

Unit 2 - Volume of Cuboid

Cuboid 

Unit 1 - Compound Interest

Compound interest is when the interest is added on each year.
The formula used to work out compound interest is:

Where, P = the principle ammount (the amount invested),

and N = number of years.

Example:
£900 was placed in the bank for 2 years, at an interest rate of 4% p.a.
What was the total interest made after the 2 years??

Unit 1 - Simple Interest

When money is placed in a bank account it normally earns interest. The interest paid is a percentage of the amount deposited. (You may wish to use a calculator for Simple interest, a scientific calculator is best.)

1.) Susan invests £100 in the bank for 4 years, where simple interest was 7.5%.

=> Interest for 1 year = 7.5% x £100
                                 = £7.50

=> Simple interest for 4 years = 4 x £7.50
                                              = £30
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2.) Jack invests £2000 for 5 years at simple interest of 4% p.a (this means per annum/year)
     How much interest has he earned after the 5 years??
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3.) Mrs.Wilson invests £4500 for 9 years, with simple interest of 3.5% p.a.

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Answers:
2 -> £400
3 -> £1417

[Next - Compound Interest]