The shorter tree is 10.5 ft. tall, and casts a shadow that is 11.25 feet long. if the taller tree casts a 17.5 ft. shadow, how tall is the tree?

hello from mrbilldoesmath!

answer:

(7 x + 6 y) (49 x^2 - 42 x y + 36 y^2)

discussion:

the trick is to recognize that 343 = 7^3 and 216 = 6^3 and, in general,

a^3 + b^3 =   (a + b) (a^2 - a b + b^2).

in our case

343x^3+216y^3   =   (7x)^3 + (6y)^3

so take a = 7x and b = 6y in the above equation to get the answer.

you,

mrb

3boys + 4 girls = 7 students

3 boys to students   true   yes

4 girls to 3 boy   true     yes

3 boys to 7 girls   false   no

4 girls to 7 students   true   yes