math
posted by francis on .
tilissa was on the middle rung of a ladder.she went up 3 rungs,thendown 5 rungs and then up 7 rungs where she rested.later she climbed up the remaining 7 rungs on the ladder.how many rungs did the ladder have?

To have a middle rung, the number of rungs must be odd
e.g. if she is on rung #7, there would be 13 rungs
6 below her, and 6 above her, she is on #7
So assume she is on rung #x
so there are 2x1 rungs
x+3  5 + 7 = 2x1
x = 6
x = 6
The ladder had 2(6) 1 or 11 rungs
check:
she started at 6,
went up 3 , was on 9
went down 5, was on 4
went up 7, was on 11, the top rung
(Very dangerous to stand on the top rung of a ladder.) 
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