15. Before oil is added to a certain road surface material, the other ingredients are mixed. The mixture contains
1 answer:
Answer:
sand = 3450 pounds
3/4 inch stones =6750 pounds
1 inch stones =4800 pounds.
Step-by-step explanation:
The mixture composition is :
45% three-quarter inch stones
32% inch stones and
sand for balance
The percent here is by mass of material used.
Weight of mixture is 15,000 pounds before oil addition.
Use the percent by weight for the two types of stones and calculate real values in pounds
Formula to apply is:
Mass percent = (mass of a material/ total mass of mixture) * 100
For 3/4 inch stones it will be:
The 3/4 inch stones weigh 6750 pounds
The 1 inch stones will be
The 1 inch stones weigh = 4800 pounds
Total for the two items : 4800+6750 =11550 pounds
The sand used weighs : 15000 - 11550 = 3450 pounds
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Answer:
- P(t) = 100·2.3^t
- 529 after 2 hours
- 441 per hour, rate of growth at 2 hours
- 5.5 hours to reach 10,000
Step-by-step explanation:
It often works well to write an exponential expression as ...
value = (initial value)×(growth factor)^(t/(growth period))
(a) Here, the growth factor for the bacteria is given as 230/100 = 2.3 in a period of 1 hour. The initial number is 100, so we can write the pupulation function as ...
P(t) = 100·2.3^t
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(b) P(2) = 100·2.3^2 = 529 . . . number after 2 hours
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(c) P'(t) = ln(2.3)P(t) ≈ 83.2909·2.3^t
P'(2) = 83.2909·2.3^2 ≈ 441 . . . bacteria per hour
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(d) We want to find t such that ...
P(t) = 10000
100·2.3^t = 10000 . . . substitute for P(t)
2.3^t = 100 . . . . . . . . divide by 100
t·log(2.3) = log(100)
t = 2/log(2.3) ≈ 5.5 . . . hours until the population reaches 10,000
