Question

HELP :)
The shaded area in the diagram below shows the cross section of a pyramid intersected by a plane that passes through the apex and is perpendicular to the base. The base of the pyramid is a square of side 10 cm. Each edge of the triangular faces is 15 cm long.

Which is the best approximation of the perimeter of the cross section?

38 cm

40 cm

32 cm

42 cm

Answer 1

first solve for x in the equation below

x^2 + 5^2 = 15^2

and tell me what you get

Answer 2

x^2+25=225

Answer 3

so far, so good

Answer 4

what's next?

Answer 5

Corresponding image to @jim_thompson5910 's algebra

Answer 6

x^2=200 ??

Answer 7

so if x ^2 = 200, then what is x

Answer 8

i dont know :/

Answer 9

what undoes the square exponent?

Answer 10

division?

Answer 11

x=100?

Answer 12

@jim_thompson5910

Answer 13

no if you had 2x = 200, then you would be correct

Answer 14

but division does NOT undo squaring

Answer 15

square roots undo squaring

Answer 16

so im not sure what to do next? square root of 200?

Answer 17

yep you got it

Answer 18

so, that's the slant height

Answer 19

14.14 isnt one of my options :/

Answer 20

you add up

14.14 + 14.14 + 10

Answer 21

you have 2 lengths that are sqrt(200) = 14.14 units long of this triangle

Answer 22

38.28 :)

Answer 23

thankyou !

Answer 24

yw