The "rule of 72" says that the doubling time in years is approximately 72 divided by the interest rate in percent. To make the money grow by a factor of 4 requires that it double twice, so will take twice as long as the period to double once.
2×72/11.3 ≈ 12.7 . . . . years
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The "rule of 72" is an approximation. The actual quadrupling time for this interest rate and compounding is about 12.6 years. (The actual product of doubling time and nominal interest rate is about 71.25.)
Jake spent a total of 70 cents.
b = black-and-white = 8 cents
c = color = 15 cents
70 = 8b + 15c
he made a total of 7 copies
b + c = 7
system of equation:
70 = 8b + 15c
b + c = 7
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b + c = 7
b + c (-c) = 7 (-c)
b = 7 - c
plug in 7 - c for b
70 = 8(7 - c) + 15c
Distribute the 8 to both 7 and - c (distributive property)
70 = 56 - 8c + 15c
Simplify like terms
70 = 56 - 8c + 15c
70 = 56 + 7c
Isolate the c, do the opposite of PEMDAS: Subtract 56 from both sides
70 (-56) = 56 (-56) + 7c
14 = 7c
divide 7 from both sides to isolate the c
14 = 7c
14/7 = 7c/7
c = 14/7
c = 2
c = 2
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Now that you know what c equals (c = 2), plug in 2 for c in one of the equations.
b + c = 7
c = 2
<em>b + (2) = 7
</em><em />Find b by isolating it. subtract 2 from both sides
b + 2 = 7
b + 2 (-2) = 7 (-2)
b = 7 - 2
b = 5
Jake made 5 black-and-white copies, and 2 color copies
hope this helps
Answer:
21% of the animals are female
Step-by-step explanation:
In total:
There are 40 + 60 = 100 animals.
Female animals.
40 dogs. Of those, 15% are female. So 0.15*40 = 6.
60 cats. Of those, 25% are female. So 0.25*60 = 15.
21 female animals.
21/100 = 0.21 = 21%
21% of the animals are female
Answer:
The Answer is: The first number is -70 and the second number is -68.
Step-by-step explanation:
Let f = first number and s = second number.
The sum of both is -138:
f + s = -138
The difference is -2
f - s = -2
Solve for f:
f = -2 + s
f = s - 2
Substitute:
s - 2 + s = -138
2s = -136
s = -68, the second number
Solve for f:
f = s - 2
f = -68 - 2 = -70, the first number
Proof:
f + s = -138
-68 + (-70) = -138
-138 = -138
Then:
f - s = -2
-70 - (-68) = -2
-70 + 68 = -2
-2 = -2
Hope this helps! Have an Awesome Day!! :-)
