# math

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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?

• math -

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 2x-1 rungs

x+3 - 5 + 7 = 2x-1
-x = -6
x = 6

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.)

• math -

25

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