Points A and B are 90 km apart from each other on a highway. A car starts from A and another from B at the same time. If they go in the same direction they meet in 9 hours and if they go in opposite directions they meet in 9/7 hours. Find their speeds.
Answers
let the speed of car starting from a be 'x' km/h and speed of car starting from b be 'y' km/h
∴total distance=80 km
⇒ 1 hour 20 mins= 4/3 hour
given that when car moves in same direction,
∴distance travelled by y= 8y km
∴distance travelled by x= 8x= 80+8y
⇒equation formed is 8x=80+8y
=> 8x-8y=80
=> x-y=10 ..................1
agai for opposite direction,
∴distance travelled by x= (4/3)x
∴distance travelled by y= (4/3) y
⇒total distance covered= 4/3*x+4/3y
=> 80= 4x+4y/3
=> 240= 4x+4y
=> 60=x+y ...............2
from equation 1 and 2 we get
60=x+y ...........2
x-y=10 .........1
=> x= 10+y ..........3
after substituting the value of equation 3 in equation 2
60= 10+y+y
=> 60-10=2y
=> 50=2y
=> 25=y
⇒x=10+y=> x= 10+25=> x=35
∴the speed of car starting from a is 35km/h
∴the speed of car starting from b is 25km/h
Answer:
Step-by-step explanation:
let the speed of car starting from a be 'x' km/h and speed of car starting from b be 'y' km/h
∴total distance=80 km
⇒ 1 hour 20 mins= 4/3 hour
given that when car moves in same direction,
∴distance travelled by y= 8y km
∴distance travelled by x= 8x= 80+8y
⇒equation formed is 8x=80+8y
=> 8x-8y=80
=> x-y=10 ..................1
agai for opposite direction,
∴distance travelled by x= (4/3)x
∴distance travelled by y= (4/3) y
⇒total distance covered= 4/3*x+4/3y
=> 80= 4x+4y/3
=> 240= 4x+4y
=> 60=x+y ...............2
from equation 1 and 2 we get
60=x+y ...........2
x-y=10 .........1
=> x= 10+y ..........3
after substituting the value of equation 3 in equation 2
60= 10+y+y
=> 60-10=2y
=> 50=2y
=> 25=y
⇒x=10+y=> x= 10+25=> x=35
∴the speed of car starting from a is 35km/h
∴the speed of car starting from b is 25km/h