- Fractions and Percentages
Fractions and percentages
A fraction can be converted to decimal by dividing the numerator by its denominator. It can be changed to percentage by simply multiplying by 100.
- Change 3/8 into a decimal and percentage
- Convert 0.145 to percentage
1) 3/8 = 0.375 in decimal
3/8 x 100% = 37.5%
APPLICATION OF DECIMAL FRACTIONS AND PERCENTAGES
Consider the following examples.
- Find 15% of 2.8kg
- Express 3.3 mass a percentage of 7.5
- Find 331/3 % of8.16litres
a. 15/100 of 2.8kg
15/100 x 2.8 x 1000g
15/100 x 2800
b. 3.3/7.5 x 100/1
33/75 x 100/1
11×4 = 44%
c. 331/3% of 8.16litres
100/3 of 8.16litres
100/3 of 8.16litres
100/3 x 8.16litres
100/3 x 8.16 x 1000 (1litre=1000cm3)
100/3 x 8160
100/3 ÷100/1 x 8160
100/3 x 1/100 x 8160
1. Express1.5 as a percentage of 2.5 m
2. Find 662/3 % of2.4m
New General Mathematics, UBE Edition, chapter 1 Pages 78-79
Essential Mathematics by A J S Oluwasanmi, Chapter 1 pages 61-64
Proportion can be solved either by unitary method or inverse method. When solving by unitary method, always
- write in sentence the quantity to be found at the end.
- decide whether the problem is either an example of direct or inverse method
- find the rate for one unit before answering the problem.
- A worker gets
N900 for 10 days of work, find the amount for (a) 3 days (b) 24 days (c) x days
For 1 day =
1 day = 900/10 = N90
a. For 3 days =3 x 90 = 270
b. For 24 days = 24×90 =
c. For x days =X x 90 =
N 90 x
- Seven workers dig a piece of ground in 10 days. How long will five workers take?
For 7 workers =10 days
For 1 worker =7×10=70 days
For 5 workers=70/5 =14 days
- 5 people took 8 days to plant 1,200 trees, How long will it take 10 people to plant the same number of trees
For 5 people =8 days
For 1 person =8×5=40 days
For 10 people =40/10 =4 days
- A woman is paid
N750 for 5 days, Find her pay for (a) 1 day (b) 22 days
- A piece of land has enough grass to feed 15 cows for x days. How long will it last (a) 1 cow (b) y cows
- A bag of rice feeds 15 students for 7 days .How long would the same bag feed 10 students
Note on direct proportion: this is an example of direct proportion .The less time worked (3 days) the less money paid (#270) the more time worked (24 days) the more money paid (
N N 2,160)
Ratio behaves the same way as fraction. Ratios are often used when sharing quantities..
1. Express the ratio of 96 c: 120c as simple as possible
Solution 96c: 120c=96/120=4/5=4.5
2. Fill in the gap in the ratio of 2:7=28
let the gap be X
2/7 = X/28
7X =2 x 28
X=2 x 28/7
X=2 x 4
X = 8
- Two students shared 36 mangoes in the ratio 2:3 How many mangoes does each student get?
Total ratio =2+3=5
First share=2/5×35/1=21 mangoes
Rate is the change in one quantity to the other. Examples are 45km/hr, a km, 1 litre etc
- A car goes 160 km in 2 hrs what is the rate in km/hr?
In 2 hrs the car travels 160 km
In 1 hr the car travels 160/2=80km
Therefore the rate of the car is 80km/hr
- A car uses 10 litres of petrol to travel 74 km. Express its petrol consumption as a rate in km per litre.
10 litres =74 km
1 litres = 74/10 km
- A car factory made 375 cars in 5 days, Find its rate in cars per day.
- A car travels 126 km in 11/2 hrs. Find the rate in km per hr.
New General Mathematics, UBE Edition, Chapter 1, pages 80-85
Essential Mathematics by A J S Oluwasanmi, Chapter 1, pages 69-72
- 5 men build in 10 days, how long would it take 25 men?
(a) 3 days (b) 2 days (c) 5 days (d) 10 days
- A girl buys 7 pens for
N210. How would ten pens cost? (a)#300(b)#30(c)#3(d)#200
- Fill in the gap in m: a =16:24 (a) 10 (b) 12 (c) 4 (d) 6
- Express 90km /hr: 120km /hr as simple as possible (a) 4:3 (b) 3:4 (c) 2:3 (d) 3:2
- A factory makes
N2000 pencils in 10 days, Find its production rate of pencils per day (a) N20 per day (b) N100 per day(c) N50 per day (d) N200 per day
1. Find 50% of 3.5m
2. A bag of corn can feed 100 chicks for 12 days. How long would the same bag feed 80