Language, notation and formulas

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

# 3 Formulas

## 3.1 Word formulas

A formula is a rule or a generalisation. Word formulas – formulas that use English words rather than mathematical symbols – are so much a part of life that people often use them without realising that they are doing so. Here are some examples.

• The cost of a purchase of oranges is the price per orange times the number of oranges.

• The total cost of petrol is the price of petrol per litre times the number of litres.

• The average speed is the distance travelled divided by the time taken.

• The number of tins of paint needed to cover a wall is the area of the wall divided by the area covered by one tin of paint.

These word formulas can be written more clearly using mathematical symbols. Notice how brackets can be used for clarity.

• Cost of oranges bought = (price per orange) × (number of oranges).

• Cost of petrol = (price of petrol per litre) × (number of litres).

• Average speed = (distance travelled)/(time taken).

• Number of tins of paint needed = (area of wall)/(area covered by one tin).

Sometimes letters are used as shorthand in formulas.

### Example 7

At constant speed, ‘distance is the product of speed and time’. Write this as a word formula and then shorten it by using symbols: d for distance, s for speed and t for time.

distance = (speed) × (time)

d = s × t or d = st

MU120_4M6

### Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has nearly 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus