Question

A, b, c start from delhi at 10 am, 11 am and 12.00 towards goa and their speed are 3 km/h, 4 km/h and 5 km/h and after meeting on the way, b send back a to c with a message. At what time c will get the message ?

Answer 1

Answer:

0.25 hr = 15 min

"It says the answer should have at least 20 words...I'm too lazy to write it all down for you!"

Answer 2

at 2 : 15 pm c will get the message.

at 10 : 00 am, A ⇒3 km/h

at 11 : 00 am , B ⇒4 km/h

at 12 : 00 am, C ⇒5 km/h

distance travelled by A in 1 hour = 3km

relative velocity of B with respect to A = 4 - 3 = 1 km/h

so, time taken to meet A and B = 3km/(1km/h) = 3h

so, at 11 : 00 am + 3 hr = 2 : 00 pm , A and B meet.

in 3hrs , distance travelled by A = 3 × 4 = 12km

distance travelled by C in 2 hrs (i.e., 2: 00 pm - 12: 00am) = 5 km/h × 2hrs = 10 km

so, seperation between A and C = 12km - 10km = 2 km

and relative velocity of C with respect to A = 5 + 3 = 8 km/h

now time taken to meet A and C = 2km/(8km/h) = 1/4 hr = 15 min

hence, at 2 : 15 pm c will get the msg.