There are two ways of solving this.
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color(blue)("Method 1")Method 1
color(Brown)("Straight line graph approach")Straight line graph approach
Standard form equation" "->y=mx+c →y=mx+c
In this case:" "c=1.2"; "m=(2.20-1.20)/100 = 1/100"; "y=1.60 c=1.2; m=2.20−1.20100=1100; y=1.60
1.6=x/100+1.21.6=x100+1.2
x=(1.6-1.2)xx100" "color(purple)(-> x=0.4xx100)x=(1.6−1.2)×100 →x=0.4×100
x=40-> 40%x=40→40%
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color(blue)("Method 2")Method 2
color(Brown)("Ratios, which is the same thing as method 1 just that this fact is in disguise.")Ratios, which is the same thing as method 1 just that this fact is in disguise.
The approach is based on the principle that the gradient is constant.
100/(2.2-1.2)=x/(1.6-1.2)1002.2−1.2=x1.6−1.2
Basically this is saying that the gradient of the whole is the same gradient as part of it!
100/1=x/0.41001=x0.4
color(purple)(0.4xx100=x)0.4×100=x
x=40" " -> 40%x=40 →40%
color(green)('"NOTE THAT IS 40% OF THE $2.20 CANDY")
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color(blue)("Determine the weights of each constituent")
so 100%-40% =60% as the proportion of the $1.20 candy
Let the whole weight be w then
60/100 w=6
w=(6xx100)/60" "=" "100/10" "=" "10lb
So
color(green)("$1.20 candy amount is "6"lb"
color(green)("$2.20 candy amount is "10-6 = 4"lb"