Help on Sec 1 Question

Togogal SG

Greenview Farm is 840km away from Redbloom Florist.

At 2pm, a lorry leaves from Farm to Florist at 80km/h.

At 3pm, a motorcycle leaves from Florist to Farm at 60km/h.

How far apart are the two vehicles one hour before they meet?

nightzip SG

3pm : Lorry is 80km from Farm

4pm : Lorry is 160km from Farm

4pm : Motor is 60km from Florist

Dist apart at 4pm: 840-160-60 = 620km

Hence, every next 1 hr, dist apart will lessen by 140km.

So, they will meet at precisely 140x4hrs = 560km

So, after 5hrs, i.e. at 8pm, the distance between two vehicles are left with only 620-560= 60km

60/140 = 25 5/7mins

They will meet at 8:25:5/7 hrs.

So, at 7:25:5/7 hrs, 140x3hrs = 420km + 220km + 60km = 700km.

They are exactly at 700km 1 hr before meeting.

nightzip SG

hmm...on the other hand, think you can just use LCM, or lowest common multiple will be easier.

Togogal SG

hmmm... thanks!

Anyway, the answer's review.

Ans: 80km + 60km = 140 km

Reasoning: One hour before the two vehicles meet, they are still traveling at their given speeds towards each other). Hence when then meet, the lorry would have travel 80km, the motorcycle 60km. Hence 140km.

charlize SG

Wah sneaky.