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VARVARA [1.3K]
3 years ago
6

A train normally travels 240 km at a certain speed. One day, due

Mathematics
1 answer:
Marrrta [24]3 years ago
6 0

\large\bf{\underline\red{Good \: Afternoon♡}}

Normal-travel DATA:

distance = 240 km

rate = x km/h

time = d/r

= 240/x hrs

_______________________

Bad weather DATA:

distance = 240 km

rate = (x-20) km/h

time = 240/(x-20) hrs

______________________

Bad time - normal time = 2 hrs

240/(x-20) - 240/x = 2

120/(x-20) - 120/x = 1

120x -120(x-20) = x(x-20)

20 = x^2 -20x

x^2 - 20x - 20 = 0

x = [20 +- sqrt(20^2 - 4*1*-20)]/2

x = [20 +- sqrt(480)]/2

x = [20 +- 4sqrt(30)]/2

x = 10 +- 2sqrt(30)

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6 0
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Phyllis invested $10,500 a portion earning a simple interest rate of 9(1/5)% per year and the rest earning a rate of 9% per year
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First investment:
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Second investment:
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Total interest after one year is $957.00, therefore
0.092x + 0.09y = 957       
 or
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Also,
x + y = 10500               (2)

Subtract (2) from (1).
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Answer:
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The second investment is $4,500 at 9% rate.

7 0
3 years ago
Explain how to use properties to prove d + (8d + 1) + 7 is equivalent to 8 + 9d.
Nadya [2.5K]

Answer:

Use the associative property to move the parentheses, and the expression becomes (d + 8d) + 1 + 7. Combine like terms, and the expression becomes 9d +8. Use the commutative property to change the order of the terms, and the expression becomes 8 + 9d.

Step-by-step explanation:

7 0
4 years ago
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