Problem 1 :
Express the ratio in simplest form :
(a) 0.4 : 0.5
(b) 1.3 : 1.8
(c) 0.1 : 0.9
(d) 0.2 : 0.6
(e) 0.4 : 0.2
(f) 1.4 : 0.7
(g) 0.03 : 0.15
(h) 0.02 : 0.12
(i) 0.18 : 0.06
(j) 0.05 : 0.15
Problem 2 :
Use the fact that 1 mile is approximately the same distance as 1.6 km to convert
a) 30 miles to km
b) 21 miles to km
c) 80 km to miles
d) 20 km to miles
(a) Solution :
0.4 : 0.5
On both parts of the ratio, we have only one digit after the decimal. So, we multiply both parts of the ratio by 10.
= 0.4(10) : 0.5(10)
= 4 : 5
(b) Solution :
1.3 : 1.8
Multiply both parts of ratio by 10, we get
= 1.3(10) : 1.8(10)
= 13 : 18
It is not possible to simplify hereafter, so the answer is 13 : 18.
(c) Solution :
0.1 : 0.9
Multiply both parts of ratio by 10, we get
= 0.1(10) : 0.9(10)
= 1 : 9
So, the answer is 1 : 9.
(d) Solution :
0.2 : 0.6
Multiply both parts of ratio by 10, we get
= 0.2(10) : 0.6(10)
= 2 : 6
= 2/6
= 1/3
So, the answer is 1 : 3.
(e) Solution :
0.4 : 0.2
Multiply both parts of ratio by 10, we get
= 0.4(10) : 0.2(10)
= 4 : 2
= 4/2
= 2/1
So, the answer is 2 : 1.
(f) Solution :
1.4 : 0.7
Multiply both parts of ratio by 10, we get
= 1.4(10) : 0.7(10)
= 14 : 7
= 14/7
= 2/1
So, the answer is 2 : 1.
(g) Solution :
0.03 : 0.15
Multiply both parts of ratio by 100, we get
= 0.03(100) : 0.15(100)
= 3 : 2
= 4/2
= 2/1
So, the answer is 2 : 1.
(h) Solution :
0.02 : 0.12
Multiply both parts of ratio by 100, we get
= 0.02(100) : 0.12(100)
= 2 : 12
= 2/12
= 1/6
So, the answer is 1 : 6.
(i) Solution :
0.18 : 0.06
Multiply both parts of ratio by 100, we get
= 0.18(100) : 0.06(100)
= 18 : 6
= 18/6
= 3/1
So, the answer is 3 : 1.
(j) Solution :
0.05 : 0.15
Multiply both parts of ratio by 100, we get
= 0.05(100) : 0.15(100)
= 5 : 15
= 5/15
= 1/3
So, the answer is 1 : 3.
Problem 2 :
Use the fact that 1 mile is approximately the same distance as 1.6 km to convert
a) 30 miles to km
b) 21 miles to km
c) 80 km to miles
d) 20 km to miles
Solution :
1 mile = 1.6 km -----(1)
a) 30 miles to km
Multiplying (1) by 30 on both sides
30 miles = 1.6 x 30 km
= 48 km
b) 21 miles to km
Multiplying (1) by 21 on both sides
21 miles = 1.6 x 21
= 33.6 km
c) 80 km to miles
From (1),
1 mile = 1.6 km
1 km = 1/1.6 mile
1 km = 0.625 miles ------(2)
Multiplying (2) by 80 on both sides
80 km = 0.625 x 80 miles
= 50 miles
d) 20 km to miles
Multiplying (2) by 20 on both sides
20 km = 0.625 x 20 miles
= 12.5 miles
Problem 3 :
If £1 is worth of $1.60 convert
a) £15 to dollars
b) $8 to pounds
Solution :
The value of £1 = $1.60 -------(1)
a) £15 to dollars
To find the value of £15, we will multiply (1) by 15 on both sides.
£1 x 15 = $1.60 x 15
£15 = $24
b) $8 to pounds
To convert dollars to pounds, we have to find the value of $1 in pounds.
$1.60 = £1
$1 = £1/1.60
$1 = £0.625 ------(2)
Multiplying (2) by 8 on both sides, we get
$1 x 8 = £0.625 x 8
$8 = £5
Problem 4 :
If 25 floppy disc cost $5.50. Calculate the cost of 11 floppy discs.
Solution :
Cost of 25 floppy disc = $5.50
Cost of 1 floppy disc = 5.50/25
= $0.22
Cost of 1 floppy disc = $0.22
Cost of 11 floppy disc = 0.22 x 11
= $2.42
Problem 5 :
Anna has 75 pence. Rashid has £1.20. What is the ratio of Rashid's money to Anna's money ?
Solution :
100 pence = £1
Amount Anna has = 75 pence
Amount Rashid has = £1.20
Converting into pence,
1.20 x 100 ==> 120 pence
Ratio between Rashid's money to Anna's money
= 120 : 75
= 120/75
= 24/15
= 8/5
So, the ratio between their money is 8 : 5.
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