Share 3.3 Application of Linear Equations
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A boy is 4 times as old as his sister. In 6 years, the sum of their ages will be 50. How old is the boy now?
(x+6) + (4x+6) = 50 Boy = 32
The sum of three consecutive even numbers is 54. What are the numbers?
16, 18, 20
A girl walks 3 km/h for 40 minutes and then runs for 20 minutes. If she travelled 5 km total, what was her running speed?
3. Walk: 3×(40/60)=2 km; run distance = 3 km r × (20/60) = 3 → r=9 km/h → 9 km/h
A father is 27 years older than his son. In 8 years, the father will be twice the son’s age. Find the father’s age now.
Let son = x, father = x+27 → Father = 43
Three consecutive even numbers add up to 84. What are the numbers?
26, 28, 30
A man is twice as old as his daughter. In 12 years, the sum of their ages will be 84. How old is he now?
Father = 46
The sum of three consecutive even numbers is 66. Find the numbers.
20, 22, 24
A student cycles 10 km/h for 24 minutes, then walks for 36 minutes. If the total distance was 8 km, find the walking speed.
Cycle: 10×(24/60)=4 km → walk = 4 km speed × (36/60)=4 → speed=6.67 km/h → 6.7 km/h
A father is 3 times as old as his son. In 5 years, the sum of their ages will be 100. Find the son's age now.
Son = 20
Three consecutive even numbers add up to 48. Find the numbers.
14, 16, 18
