SOLUTION: . to travel from singapore to kuala lampur ,a distance kf 390km , motoridt finds that if he travels 6 km/h faster than its usual average speed,he will take 15 minutes less ti compl

Question 1011058: . to travel from singapore to kuala lampur ,a distance kf 390km , motoridt finds that if he travels 6 km/h faster than its usual average speed,he will take 15 minutes less ti complete his usual journey . Calculate the usual avergae speed of the motorist
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!
This form of travel rates problem is common as an exercise.

rate time distance IF r+6 t-1/4 390 Usual r t 390

rate time distance IF r+k t-h d Usual r t d

Be sure you understand what is happening in and between the two data tables above.

------formula for t in terms of r

-----quadratic equation in the unknown variable, r.
You can use the formula for general solution of a quadratic equation and try to simplify
that, if at all possible, ... or you can simply substitute the given, known values for h
, k, and d, now and then deal with the resulting form of quadratic equation.

----now the quadratic equation is less general, fewer symbols.

----you need the PLUS form.

Do whatever you need with this value.

--
347 and 3 both are prime numbers. Decimal approximate for the solution is .
Answer by MathTherapy(10552) (Show Source): You can put this solution on YOUR website!
. to travel from singapore to kuala lampur ,a distance kf 390km , motoridt finds that if he travels 6 km/h faster than its usual average speed,he will take 15 minutes less ti complete his usual journey . Calculate the usual avergae speed of the motorist

Let usual speed be S
Then hypothetical speed = S + 6
We then get the following TIME equation: _______
390(4)(S + 6) = 390S(4) + S(S + 6) -------- Multiplying by LCD, 4S(S + 6)

Continue to solve for S, the usual speed, ignoring the negative (< 0) value for S
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