Check the picture below.
assuming both hyperbolas at centered at the origin, the values for the numerator and denominator will switch, so that the slope of one is the reciprocal of the other's slope.
Let x be the required waranty period, then
P(X < x) = P(z < (x - 12)/(8/12)) = 1 - 0.067 = 0.933
P(z < 12(x - 12)/8) = P(z < 1.498)
12(x - 12)/8 = 1.498
x - 12 = 8(1.498) / 12 = 0.9987
x = 12 - 0.9987 = 11
Therefore, they should waranty for 11 years so that no more than 6.7% fail within that time.
cost of production = %13
Let the price be p, then
revenue less price of failed iron = p - 0.067(13) = p - 0.871
Profit = p - 0.871 - 13 = 5
p - 13.871 = 5
p = 5 + 13.871 = 18.871
Therefore, the should charge $18.87 per waffle iron.
Answer:
.
Step-by-step explanation:

Step-by-step explanation:
4/5 gallons for 280 ft² (the ² is missing in the question ...).
3 gallons would be 15/5.
so, what do I need to multiply 4 with to get 15 ?
4×x = 15
x = 15/4
multiplying now also 280 ft² with this factor gives us the answer :
280 × 15/4 = 70 × 15 = 1050 ft²
they can paint 1050 ft² with 3 gallons of paint.