AC Lim's answer to OBAMA's Primary 6 Maths Speed Singapore question.
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Distance = 400m
Total speed = 90+110 =200 m/min
Time taken to meet = 400÷200 = 2 mins
a) Aileen speed 1 min → 90m
2 mins = 180m
b) From a, 2 mins = 180m.
Aileen travelled 180m
So Betty travelled 220m
The different distance travelled between them for each meet increased 40m.
Therefore 400m take 400÷40= 10 times to meet again at starting point.
1 time→2 mins
10 times →20 mins
Ans = 18 mins later they will meet at starting point after 1st meet.
Hope this helps
Total speed = 90+110 =200 m/min
Time taken to meet = 400÷200 = 2 mins
a) Aileen speed 1 min → 90m
2 mins = 180m
b) From a, 2 mins = 180m.
Aileen travelled 180m
So Betty travelled 220m
The different distance travelled between them for each meet increased 40m.
Therefore 400m take 400÷40= 10 times to meet again at starting point.
1 time→2 mins
10 times →20 mins
Ans = 18 mins later they will meet at starting point after 1st meet.
Hope this helps
Date Posted:
5 years ago
Can you share the answer?
The answer for b) is 40 min.
So this should be the working...
Distance = 400
Total speed = 90+110 =200
Time taken to meet = 400÷200 = 2 mins
a) Aileen speed 1 min → 90m
2 mins = 180m
b) From a, 2 mins = 180m.
So, Betty 2 mins = 220m
When Betty pass the starting point for 2nd meet, they are 40m away from starting in 4 mins.
The different distance between them to starting point is 40m in 4 mins.
Therefore 400m take 400÷40×4=40 mins.
Distance = 400
Total speed = 90+110 =200
Time taken to meet = 400÷200 = 2 mins
a) Aileen speed 1 min → 90m
2 mins = 180m
b) From a, 2 mins = 180m.
So, Betty 2 mins = 220m
When Betty pass the starting point for 2nd meet, they are 40m away from starting in 4 mins.
The different distance between them to starting point is 40m in 4 mins.
Therefore 400m take 400÷40×4=40 mins.
How about another question? Bus interchange meet again at 9.00am?
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