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Question

Answer

Method 1 :

Town P —————————— 216 km —————————- Town Q
0710, Timothy ——-> …………………………..… <——- 08 30, Steven

0710 ——- 80 min ——- 0830
216/3 = 72 (distance Steven travelled)
216 – 72 = 144 (distance Timothy travelled)

Timothy’s speed : Steven’s speed
4 : 3

(72/3) x 4 = 96 (distance Timothy travelled from 0830 till meeting Steven)
144 – 96 = 48 (distance Timothy travelled from 0710 to 0830)
48/(80/60) = 64

 

Method 2 :

Town P ————————————- 216 km ———————————– Town Q
0710, Timothy ——-> ………………………………………………………… <——- 08 30, Steven

0710 ——- 80 min ——- 0830
total distance Steven travelled = 3u = 216/3 = 72
total distance Timothy travelled = 6u = 216 – 72 = 144

Timothy’s speed : Steven’s speed
4 : 3

distance travelled by Timothy from 0710 to 0830 = 144/(6 – 4) x 2 = 48
48/(80/60) = 64

Ans : 64 km/h.

1 Reply 0 Likes

Mr. Alfretztay, 

Please help to clarify: 

0710 ——- 40 min ——- 0830   — Is this not 80 mins ?

(72/3) x 4 = 96 (distance Timothy travelled form 0830 till meeting Steven) –  May I know why 72 needs to be divided by three and multiplied by 4.  It is not clear to me.

Thanks for the help. 

 

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Please refer to my replies in brackets.

“Please help to clarify:
0710 ——- 40 min ——- 0830 — Is this not 80 mins ? (Yes, it is indeed 80 min)
(72/3) x 4 = 96 (distance Timothy travelled form 0830 till meeting Steven) – May I know why 72 needs to be divided by three and multiplied by 4. It is not clear to me. (I have presented an alternative solution and hope that it will aid you in your understanding.)
Thanks for the help. (You are welcome.)”

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8h30m – 7h10m = 1h20m = 4/3 hr

216 / 3 = 72
72 x 2 = 144
4/3 x 72 = 96
144 – 96 = 48
48 / (4/3) = 64 km/h as the answer

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This is a Distance Speed Time question. 

  Time    Speed     Distance 
Tim   144/4u   4u 144
Steven  72/3u   3u 72
      216

216 ÷ 3 = 72

72 × 2 = 144

144/4u – 72/3u  =  80/60   (their time difference)

432/12u  – 288/12u = 4/3

(432 – 288)/12u = 4/3

144 × 3    = 4 × 12u

48u = 432

1u = 432 ÷ 48 = 9

4u = 4 × 9 = 36 km/h

 

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how u got 144/4u – 72/3u = 80/60 (their time difference)

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Checking

144 ÷ 36 = 4 hour

72 ÷ 27 = 2 2/3 hour

Time difference = 4 – 2 2/3 = 1 1/3 = 1 hr 20 min

 

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