If t is the amount of time she used it, then it lost t*(5/min) percentage points; then she charged it for 2t, so it gained (2t)*(2/min) =t*(4/min) percentage points.
This means that above this time period, the phone lost t*(5/min)-t*(4/min) =t*(1/min) percentage points; because this loss is recognized to be 10 percentage points, this means t*(1/min) =10, so t=10 min.
This means that she used her phone for 10 minutes and charged it for 20 minutes.
Answer:
Step-by-step explanation:
The inequality to find the maximum number of t-shirts is:

Step-by-step explanation:
Debbie has at most $60 to spend
Then it will be <=60
Now she has to spend 22 dollars on jeans so 22 will be add to the initial amount for sure.
And
Let x be the number of t-shirts
Then the cost of x t-shirts will be 8x
Putting this in to inequality will be:

The inequality to find the maximum number of t-shirts is:

Keywords: Inequality
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1/4= 0.25
2/4= 1/2 = 0.5
0.25 x 0.5 = 0.125
0.125 = 1/8
C(x) = 400 + 20x - 0.2x²
c(30) = 400 + 20(30) - 0.2(30)²
= 400 + 600 - 0.2(900)
= 1000 - 180
= 820
It costs $820 when 30 radios are produced.
Marginal cost is how much it would cost to make one MORE of the same product so now we find how much it costs to produce 31 radios and compare the two.
c(31) = 400 + 20(31) - 0.2(31)²
= 400 + 620 - 0.2(961)
= 1020 - 192.2
= 827.8 or ≈828.
Now we find the difference which means we subtract the two.
828 - 820 = 8.
Your marginal cost is $8.
To compare we can also do 29 radios.
c(29) = 400 + 20(29) - 0.2(29)² = 811.8 or ≈812
820 - 812 = 8.