C. 60: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60
1,000: 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 125, 200, 250, 500, 1000
Now we find the common numbers. One doesn’t count as when multiplied later on, it will not change anything.
60: 2, 4, 5, 10, 20
1,000: 2, 4, 5, 10, 20
The highest common factor is 20 because it’s, well, the highest number.
D. Do the same thing for D.
24: 1, 2, 3, 4, 6, 8, 12, 24
880: 1, 2, 4, 5, 8, 10, 11, 16, 20, 22, 40, 44, 55, 80, 88, 110, 176, 220, 440, 880
20 and 880: 2, 4, 8
8 is the Highest Common Factor.
E. Do the same thing with E.
90: 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90
1,000: 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 125, 200, 250, 500, 1000
90 and 1000: 2, 5, 10
10 is the Highest Common Factor.
Let x be the length of the train.
On the basis of the observer;
Speed of the train = x/6
On the basis of the bridge;
Total distance covered by any point of the train= 350+x
Speed = (350+x)/20
Equating the two expressions of speed;
x/6 = (350+x)/20
20(x) = 6(350+x)
20x = 2100+6x
(20-6)x = 2100
14x = 2100
x= 2100/14 = 150 m
Speed = x/6 = (350+x)/20 = 150/6 = 500/20 = 25 m/s.
Therefore,
Length of train = 150 m
Speed of train = 25 m/s
