a car averages 55 mph for the first 4 hours of a trip and averages 70 mph for each additional hour . the average speed for the entire trip was 60 mph . how many hours long is the trip ?
"in 4 hr journey = 55 * 4 = 220 mph let in the next additional hour journey = 70 * x = 70 x mph so , ( 220 + 70 x ) / ( 4 + x ) = 60 = > 220 + 70 x = 240 + 60 x = > 10 x = 20 = > x = 2 h so the trip is ( 4 + x ) = > 6 hours long answer : a"
add(divide(subtract(multiply(60, 4), multiply(55, 4)), subtract(70, 60)), 4)