The obstacle course was very challenging. Three out of every 8 contestants fell in the mud at the beginning and gave up. Then 1 out of 5 couldn't climb over the wall. Then 2 out of 9 couldn't climb up the rope and dropped out. Finally, 1 out of 10 couldn't jump over the hurdles and quit. What percent of the contestants made it to the finish line?

35%

Explanation:

Let us assume that the number of contestants = N.

The fractions are given as - -

"3 out of 8"

"1 out of 5"

"2 out of 9"

"1 out of 10"

Hence the no. of contestants in the competitions is in the multiples of 8, 5, 9 and 10.

Therefore the least common multiple of the numbers 8, 5, 9 and 10 is 360.

Therefore the number of contestants should be a multiple of 360.

Now, let N = 360 p

Firstly, 3 out of 8 students fell and gave up and so remaining 5 out of 8 passed. That is (5/8) x 360 p = 225 p passed.

Secondly, 1 out of 5 could not climb. Therefore, remaining 4 out of 5 climbed and passed. That is (4/5) x 225 p = 180 p passed.

Thirdly, 2 out of 9 dropped out. Thus remaining 7 out of 9 passed. That is (7/9) x 180 p = 140 p passed.

Fourthly, 1 out of 10 could not jumped and quit. Thus remaining 9 out of 10 passed. Therefore, (9/10) x 140 p = 126 p passed.

Therefore now fraction who finished is = 126 p / 360 p

= 126 / 360

= 21 / 60

= 7/20

Thus the fraction that finished is 7 / 20

Therefore percentage that finished is (7/20) x 100 = 35%

Thus 35% of the contestant made to the finish line.