25 because 5 (the number of sticks) times 5 (the number of houses) equals 25
Roberto overtakes Juanita at the rate of (7.7 mi)/(11 h) = 0.7 mi/h. This is the difference in their speeds. The sum of their speeds is (7.7 mi)/1 h) = 7.7 mi/h.
Roberto walks at the rate (7.7 + 0.7)/2 = 4.2 mi/h.
Juanita walks at the rate 4.2 - 0.7 = 3.5 mi/h.
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In a "sum and diference" problem, one solution is half the total of the sum and difference. If we let R and J be the respective speeds of Roberto and Juanita, we have
R + J = total speed
R - J = difference speed
Adding these two equations, we have
2R = (total speed + difference speed)
R = (total speed + difference speed)2 . . . . . as computed above
1) 2.4
2) 6.4
3) 7.7
4) 9.9
5) 2.8
Hope it helps <3
Just basic simplification, make 1 of the variable alone on one side
12 packs would cost $3.96 if you multiply .33 and 12<span />
