Decimal Addition/Subtraction
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ISEE Lower Level: Mathematics Achievement › Decimal Addition/Subtraction
The total length of three wooden planks is 8.5 meters. The first plank is 2.75 meters long, and the second plank is 3.5 meters long. What is the length of the third plank?
6.25 meters
2.25 meters
5.00 meters
5.75 meters
Explanation
First, add the lengths of the two known planks: 2.75 meters + 3.50 meters = 6.25 meters. Then, subtract this sum from the total length to find the length of the third plank: 8.50 meters - 6.25 meters = 2.25 meters.
A rectangular garden is 12.5 meters long and 7.85 meters wide. A fence is to be built around three sides of the garden, leaving one of the longer sides open. What is the total length of the fence needed?
40.7 meters
28.2 meters
20.35 meters
32.85 meters
Explanation
The fence will cover the two shorter sides (widths) and one longer side (length). The total length is the sum of these three sides: 7.85 meters + 7.85 meters + 12.5 meters. First, add the widths: 7.85 + 7.85 = 15.7 meters. Then add the length: 15.7 + 12.5 = 28.2 meters.
After spending $4.75 on lunch and $2.50 on a snack, Maria had $7.80 left. How much money did Maria have to begin with?
$0.55
$10.30
$12.55
$15.05
Explanation
To find the starting amount, you must add the money she spent to the money she has left. First, find the total amount spent: $4.75 + $2.50 = $7.25. Then, add the amount left to the total spent: $7.25 + $7.80 = $15.05.
David starts with $20.00 and buys a book for $11.45. Emily starts with $15.00 and buys a movie ticket for $7.80. What is the difference between the amount of money David has left and the amount Emily has left?
$1.35
$3.65
$5.00
$15.75
Explanation
First, calculate the money each person has left. David has $20.00 - $11.45 = $8.55 left. Emily has $15.00 - $7.80 = $7.20 left. Then, find the difference between their remaining amounts: $8.55 - $7.20 = $1.35.
A seedling was 5.8 centimeters tall at the beginning of the week. By the end of the week, it was 8.25 centimeters tall. How much did the seedling grow during the week?
2.45 cm
2.55 cm
3.45 cm
14.05 cm
Explanation
To find the amount of growth, subtract the initial height from the final height. Remember to align the decimal points by treating 5.8 as 5.80. The calculation is 8.25 cm - 5.80 cm = 2.45 cm.
A baker starts with a 10-kilogram bag of flour. He uses 1.75 kg for bread, 0.9 kg for cookies, and 2.45 kg for cakes. What was the total decrease in the weight of the flour in the bag?
5.80 kg
4.20 kg
4.90 kg
5.10 kg
Explanation
The question asks for the total decrease, which is the total amount of flour used. To find this, add the weights of the flour used for each item: 1.75 kg + 0.90 kg + 2.45 kg = 5.10 kg.
The average monthly rainfall for a town is 12.5 centimeters. This month, it rained 3.25 cm the first week, 2.8 cm the second week, and 4.15 cm the third week. How much more rain is needed in the fourth week to meet the monthly average?
2.3 cm
9.25 cm
7.45 cm
10.2 cm
Explanation
First, find the total rainfall for the first three weeks: 3.25 cm + 2.80 cm + 4.15 cm = 10.20 cm. Then, subtract this total from the average monthly rainfall to find out how much more is needed: 12.50 cm - 10.20 cm = 2.30 cm.
A tank contains 50.5 liters of water. A pump removes 12.75 liters. Then, an additional 8.5 liters are drained from the tank. How many liters of water are left in the tank?
37.75 liters
21.25 liters
29.25 liters
29.75 liters
Explanation
First, find the total amount of water removed by adding the two amounts: 12.75 liters + 8.50 liters = 21.25 liters. Next, subtract the total amount removed from the starting amount of water: 50.50 liters - 21.25 liters = 29.25 liters.
A recipe for trail mix calls for 0.75 kilograms of peanuts, 0.5 kilograms of raisins, and 0.35 kilograms of chocolate chips. If the empty container for the mix weighs 0.12 kilograms, what is the total weight of the container filled with trail mix?
1.48 kg
1.72 kg
1.77 kg
1.60 kg
Explanation
First, find the total weight of the trail mix ingredients by adding them together: 0.75 kg + 0.50 kg + 0.35 kg = 1.60 kg. Then, add the weight of the empty container to the weight of the ingredients to find the total weight: 1.60 kg + 0.12 kg = 1.72 kg.
Juan is 1.52 meters tall. His older sister, Sofia, is 1.68 meters tall. His younger brother, Mateo, is 1.35 meters tall. What is the sum of the difference in height between Sofia and Juan, and the difference in height between Juan and Mateo?
4.55 m
0.16 m
0.33 m
0.01 m
Explanation
This problem can be solved in two steps. First, find the difference in height between Sofia and Juan: 1.68 m - 1.52 m = 0.16 m. Second, find the difference in height between Juan and Mateo: 1.52 m - 1.35 m = 0.17 m. Finally, add these two differences together: 0.16 m + 0.17 m = 0.33 m. Alternatively, notice that this sum is equal to the total difference in height between the tallest (Sofia) and the shortest (Mateo): 1.68 m - 1.35 m = 0.33 m.