Solve. Martha can rake the leaves in her yard in 3 hours. Her younger brother can do the job in 4 hours. How long will it take them to do
the job if they work together?

3.5 hours

Step-by-step explanation:

all u have to do is add 3+4=7 then 7 divided by 2 which equals 3.5

800 cm²

Step-by-step explanation:

Given similar figures with ratio of sides = a : b

Then ratio of areas = a² : b²

Here ratio of sides = 20 : 6 = 10 : 3, thus

ratio of areas = 10² : 3² = 100 : 9 = , thus

area of Δ DEF = × 72 = 100 × 8 = 800 cm²