Select 222 strategies that we can use to subtract 971-868971−868971, minus, 868. Choose 2 answers:
Choose 2 answers:

(Choice A)
A
Add 3+1003+1003, plus, 100.

(Choice B)
B
Add 800+60+8800+60+8800, plus, 60, plus, 8.

(Choice C)
C
Subtract 973-870973−870973, minus, 870.

geometry: triangles

solvers

lessons

answers archive

call the larger triangle abc

then the smaller triangle cde is similar to abc (all angles are equal, aaa).  

ab is the side that is 36, and we wish to find de, the side corresponding to ab

area_cde = area_abc - area_cde --> area_abc / area_cde = 2

let x=length of de

ratio of areas = (ratio of sides)^2

+2+=+%2836%2fx%29%5e2+

+2+=+1296%2fx%5e2+

++x%5e2+=+1296%2f2+=+648+

25.45584

so mark-up is 0.4 multiplied by 180 = 72

the one where 1 and 2 are directly across from each other.  

see image