If you're asking how this is possible,
Answer and explanation:
If Sandy and Allen's mother does the job in 5 hours
And Allen and Sandy's contributions completes the job in 2.5 hours
5 hours - 2.5 hours =2.5 hours
Allen and Sandy's contribution is half of the time it took only Allen and Sandy's mother= 2.5 hours
Therefore Allen and Sandy together will take 2.5×2 = 5 hours to complete the job alone without their mother
A similar example: if it takes one person 2 hours to peel 5 potatoes and it takes 1 hour to peel same number of potatoes if a second person helps, then this second person reduces the time used by 1 hour(50%) and would take 2 hours to complete the work.
This is the concept of simultaneous equations, the question requires us to solve the system of equations given by:
2x+4y=38
10x+3y=105
from the top equation;
2x=38-4y
dividing through by 2 we get:
x=19-2y......(*)
substituting (*) in the second equation we get:
10x+3y=105
10(19-2y)+3y=105
190-20y+3y=105
collecting like terms we get:
-20y+3y=105-190
-17y=-85
dividing both sides by -17 we get:
(-17y)/(-17)=(-85)/(-17)
y=5
thus
x=19-2y
x=19-2*5
x=19-10
x=9
thus
x=9 and y=5
Answer:
A. 2.3km
Step-by-step explanation:
Since 2cm = 1km
4.6cm = xkm
xkm = 4.6 x 1 / 2
= 2.3km
Answer: the bottom rectangle is 21 square units
The top triangles are each 6 square units
Step-by-step explanation:
Do 6 times 3.5 to find area of rectangle
Then do 3 times 4 divided by 2 for each of the top triangles
