ACT Math : Decimals
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Example Question #41 : Decimals
Simplify the following:
To add decimals, first add zeros to the necessary terms so they all have the same number of places to the right of the decimal point.
Now, temporarily drop the decimal and add the numbers as if they were whole numbers.
Finally, add the decimal place back in, in the same place you removed it from. In this case, we originally modified our numbers so they all had 3 numbers to the right of the decimal, so we will add the decimal back to the exact same place. Thus, our answer is:
Example Question #1 : How To Add Decimals
Add:
Rewrite the problem so that the tenths, hundredths, and thousandths digits align. Use zeros as placeholders and solve.
Example Question #2 : How To Add And Subtract Decimals
A runner runs 10.2 miles east, then 2.3 miles west, then 1.4 miles east.
How many miles did the runner travel from where he started? (How far east did the runner go)?
13.9 miles
10.2 miles
9.3 miles
19.3 miles
6.5 miles
9.3 miles
When the runner is travelling east, it's in the positive direction. West is the negative direction. So we can compute it by doing the operation 10.2 + (–2.3) + 1.4 = 9.3
Example Question #1 : How To Add And Subtract Decimals
What is 
Example Question #2 : How To Add And Subtract Decimals
Subtract:
Rewrite 
Example Question #1 : How To Multiply Decimals
If Exam 1 is worth 25% of the total grade, Exam 2 is worth 25% and Exam 3 is worth 50%, what is Dave’s final grade?
84
83.5
82
79
85.75
84
Final Grade = Exam1 * 0.25 + Exam 2 * 0.25 + Exam3 * 0.50 =
96*0.25 + 70*0.25 + 85*0.5 =
24 + 17.5 + 42.5 = 84
Example Question #1 : How To Multiply Decimals
A chemistry students needs to dilute some acid. How much water should be added to 2 L of 80% acid solution to yield 50% acid solution?
1.0 L
2.0 L
0.8 L
1.5 L
1.2 L
1.2 L
Pure water would be 0% solution and pure solution would be 100%
V1P1 + V2P2 = VfPf
Let x = amount of water to add
x(0) + 2(0.80) = (x + 2)(0.50) which when solved gives x = 1.2 L
Example Question #1 : Fluently Add, Subtract, Multiply, And Divide Multi Digit Decimals: Ccss.Math.Content.6.Ns.B.3
Kevin is looking at the blueprint of the house he is building. The scale is 1 inch = 5 feet. On paper, the master bedroom is 2.5 inches by 3 inches. What is the actual size of the bedroom?
10 ft x 10 ft
12.5 ft x 15 ft
15 ft x 25 ft
20 ft x 30 ft
7.5 ft x 9 ft
12.5 ft x 15 ft
The given dimensions must be multiplied by 5, so 2.5 inches becomes 12.5 feet, and 3 inches becomes 15 feet.
Example Question #44 : Decimals
If 
Using the factor-label method we get the following equation.
We treat the units as if they are numbers, and can cancel the units from the fractions.
Example Question #2 : How To Multiply And Divide Decimals
A car has gas mileage of 46 miles per gallon. Assume that gas costs $3.90 per gallon. What would be the total cost of gas if the car traveled 1,150 miles?
$97.50
$125.70
$179.40
$100.00
$115.60
$97.50
First find out how many gallons of gas the car consumed while traveling 1150 miles. This can be found out like so:
1150 miles x gallons/46 miles = 25 gallons
Multiplying 25 by $3.90 yields $97.50.
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