Mathematical and Physical Journal
for High Schools
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Problem K. 420. (March 2014)

K. 420. Alex drives 63 km to work each morning. If he starts 20 minutes later than usual, his journey will take 40% more time because of the traffic jam, and thus his average speed is reduced to 36 km/h. How long does Alex take to drive to work if he starts at the usual time?

(6 pont)

Deadline expired on April 10, 2014.


Sorry, the solution is available only in Hungarian. Google translation

Megoldás. 63 km-t 36 km/h átlagsebességgel megtéve az ehhez szükséges idő 63:36=1,75 óra. Ez 40%-kal több, mint a szokásos menetidő, ami ezek szerint 1,75:1,4 = 1,25 óra.


Statistics:

167 students sent a solution.
6 points:153 students.
4 points:1 student.
2 points:5 students.
1 point:1 student.
0 point:5 students.
Unfair, not evaluated:2 solutions.

Problems in Mathematics of KöMaL, March 2014