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In A B C ,\ D ,\ E\ a n d\ F are, respe...

In ` A B C ,\ D ,\ E\ a n d\ F` are, respectively, the mid-points of `B C ,\ C A\ a n d\ A B` . If the lengths of side `A B ,\ B C\ a n d\ C A` are 7cm, 8cm, and 9cm, respectively, find the perimeter of ` D E F`

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as we know EF is a line joining mid point of AB, AC is parallel to BC and
EF`=(1/2)xxBC`
`=(1/2)xx8=4cm`
similarly,DE`=(1/2)xx7=7/2cm`
and DF`=9/2cm`
perimeter of DEF `=7/2+9/2+4`
`=12cm`
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