John jogs on track A at 6 kmph and Mary jogs on track B at 7.5 kmph. T

1.	John jogs on track A at 6 kmph and Mary jogs on track B at 7.5 kmph. The total length of tracks A and B is 325 metres. While john makes 9 rounds of track A, mary makes 5 rounds of track B. In how many seconds will Mary make one round of track A?
Answer» Calculation: Let the track length for John be x km And Mary for be y km Distance travelled by John = 9x meters And Distance travelled by Mary = 5y meters Now, Time taken by John = (9x/6) hours Time taken by Mary = (5y/7.5) hours According to the question: Time taken by John = Time taken by Mary ⇒ (9x/6) = (5y/7.5) ⇒ (3x/2) = (2y/3) ⇒ x = (4y/9) ----(1) Total track length = 325 meters ⇒ (y/9) + y = 325 ⇒ (4y + 9y)/9 = 325 ⇒ (13y/9) = 325 ⇒ y = (325 × 9)/13 ⇒ y = 225 Now, putting the value of y = 225 in equation (1): ⇒ x = (4y/9) ⇒ x = (4 × 225)/9 ⇒ x = (4 × 225)/9 = 100 meters Time taken by Mary = [100/(7.5 × 5/18)] ⇒ [(1000 × 18)/(7.5 × 5)] = 48 seconds ∴ Time taken by Mary is 48 seconds.

John jogs on track A at 6 kmph and Mary jogs on track B at 7.5 kmph. The total length of tracks A and B is 325 metres. While john makes 9 rounds of track A, mary makes 5 rounds of track B. In how many seconds will Mary make one round of track A?

Answer»

Calculation:

Let the track length for John be x km

And Mary for be y km

Distance travelled by John = 9x meters

And Distance travelled by Mary = 5y meters

Now,

Time taken by John = (9x/6) hours

Time taken by Mary = (5y/7.5) hours

According to the question:

Time taken by John = Time taken by Mary

⇒ (9x/6) = (5y/7.5)

⇒ (3x/2) = (2y/3)

⇒ x = (4y/9) ----(1)

Total track length = 325 meters

⇒ (y/9) + y = 325

⇒ (4y + 9y)/9 = 325

⇒ (13y/9) = 325

⇒ y = (325 × 9)/13

⇒ y = 225

Now, putting the value of y = 225 in equation (1):

⇒ x = (4y/9)

⇒ x = (4 × 225)/9

⇒ x = (4 × 225)/9 = 100 meters

Time taken by Mary = [100/(7.5 × 5/18)]

⇒ [(1000 × 18)/(7.5 × 5)] = 48 seconds

∴ Time taken by Mary is 48 seconds.