Exercise: Foundational Math
Questions for: Arithmetical Fractions
A school project requires students to dedicate a certain amount of time each week. Maya plans to spend 3/4 of her total study time on mathematics. Within that math study time, she will devote 2/3 of it specifically to geometry problems.
What fraction of her total study time will Maya dedicate to geometry problems?
A: 1/2
B: 1/4
C: 5/7
D: 17/12
Answer: A
To find a fraction of a fraction, you multiply the two fractions.
Maya dedicates 3/4 of her total time to mathematics.
She dedicates 2/3 of that mathematics time to geometry problems.
So, the fraction of total study time dedicated to geometry is (2/3) * (3/4).
Multiply the numerators: 2 * 3 = 6.
Multiply the denominators: 3 * 4 = 12.
This results in the fraction 6/12.
Simplify the fraction: 6/12 simplifies to 1/2.
Why others are wrong:
A โ Correct answer.
B โ This could result from calculating the remaining fraction (1 - 2/3 = 1/3) and then multiplying it by 3/4, misinterpreting the question's intent.
C โ This is an error made by adding the numerators (2+3) and denominators (3+4) directly, which is not a valid operation for multiplying fractions.
D โ This is the result of adding the two fractions (2/3 + 3/4 = 8/12 + 9/12 = 17/12), not multiplying them.
A construction project requires a specific amount of work. On Monday, 2/5 of the project is completed. On Tuesday, an additional 1/3 of the project is completed.
What fraction of the construction project remains to be completed?
A: 4/15
B: 11/15
C: 3/8
D: On Tuesday, an additional 1/3 of the project is completed.
What fraction of the construction project remains to be completed?
A. 4/15
B. 11/15
C. 3/8
D. 1/15
Answer: A
First, calculate the total fraction of the project completed: 2/5 + 1/3.
To add these fractions, find a common denominator, which is 15.
Convert 2/5 to an equivalent fraction with a denominator of 15: (2*3)/(5*3) = 6/15.
Convert 1/3 to an equivalent fraction with a denominator of 15: (1*5)/(3*5) = 5/15.
Add the equivalent fractions: 6/15 + 5/15 = 11/15. This is the total fraction of the project completed.
To find the fraction remaining, subtract the completed portion from the whole project (which is 1, or 15/15).
Remaining = 15/15 - 11/15 = 4/15.
Why others are wrong:
A โ Correct.
B โ This represents the total fraction of the project that has been *completed*, not the fraction that remains.
C โ This results from incorrectly adding the numerators (2+1=3) and the denominators (5+3=8) directly, without finding a common denominator.
D โ This would be the result of subtracting 1/3 from 2/5 (6/15 - 5/15 = 1/15), which incorrectly finds the difference between the two completed parts instead of their sum and then subtracting from the whole.
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A large pizza was initially cut into 8 equal slices. John consumed one-quarter of the entire pizza. Subsequently, Mary ate half of the pizza that remained after John had taken his share.
What fraction of the original pizza is left?
A: Subsequently, Mary ate half of the pizza that remained after John had taken his share.
What fraction of the original pizza is left?
A. 1/8
B: 1/4
C: 3/8
D: 1/2
Answer: C
1. The entire pizza represents 1 whole.
2. John consumed 1/4 of the pizza.
3. The fraction of pizza remaining after John's share is 1 - 1/4 = 3/4.
4. Mary then ate 1/2 of the *remaining* pizza. This means Mary ate 1/2 * (3/4) = 3/8 of the original pizza.
5. The total fraction of pizza consumed is John's share + Mary's share = 1/4 + 3/8.
6. To add these fractions, find a common denominator (8). 1/4 is equivalent to 2/8.
7. Total consumed = 2/8 + 3/8 = 5/8.
8. The fraction of the original pizza left is 1 (whole pizza) - 5/8 (consumed) = 3/8.
Why others are wrong:
A โ This would represent 1 slice remaining, indicating a miscalculation of total consumed or remaining portion.
B โ This could be the fraction remaining if John ate 1/2 and Mary ate 1/4 of the total, or a misinterpretation of "half of the remaining".
D โ This would be the amount left if only 1/2 of the pizza was consumed in total, or if Mary was the only one to eat and consumed half.
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A baker uses 3/4 cup of sugar for a large cake. If they decide to make a smaller cake that requires only 2/3 of the sugar used for the large cake, how much sugar is needed for the smaller cake?
What is the amount of sugar, in cups, required for the smaller cake?
A: 1/2 cup
B: 17/12 cups
C: 1/12 cup
D: 5/7 cup
Answer: A
The problem asks for 2/3 of the 3/4 cup of sugar.
To find a fraction "of" another fraction, you multiply them.
Multiply the numerators: 2 * 3 = 6.
Multiply the denominators: 3 * 4 = 12.
The product is 6/12.
Simplify the fraction by dividing both the numerator and denominator by their greatest common divisor, which is 6.
6 รท 6 = 1.
12 รท 6 = 2.
So, the simplified amount is 1/2 cup.
Why others are wrong:
B โ This result is obtained by incorrectly adding the two fractions (3/4 + 2/3), not by finding a fraction "of" another.
C โ This result is obtained by incorrectly subtracting the two fractions (3/4 - 2/3), not by finding a fraction "of" another.
D โ This result comes from incorrectly adding the numerators and denominators (2+3)/(3+4), which is an incorrect operation for this problem.
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A chef begins with 3 1/2 kilograms of sugar for daily use. During the day, he uses 3/4 kilogram for a dessert recipe and another 1/2 kilogram for a sauce.
What is the total amount of sugar remaining in the chef's supply at the end of the day?
A: 2 1/4 kg
B: 1 1/4 kg
C: 2 3/4 kg
D: 2 5/6 kg
Answer: A
Step 1: Calculate the total amount of sugar used.
Total used = 3/4 kg + 1/2 kg
To add these fractions, find a common denominator, which is 4.
1/2 kg can be written as 2/4 kg.
Total used = 3/4 kg + 2/4 kg = 5/4 kg.
Step 2: Convert the initial amount of sugar to an improper fraction with the common denominator.
Initial amount = 3 1/2 kg.
As an improper fraction, 3 1/2 = (3 * 2 + 1) / 2 = 7/2 kg.
To have a denominator of 4, multiply the numerator and denominator by 2: 7/2 kg = 14/4 kg.
Step 3: Subtract the total amount of sugar used from the initial amount.
Remaining sugar = 14/4 kg - 5/4 kg = 9/4 kg.
Step 4: Convert the result to a mixed number.
9/4 kg = 2 with a remainder of 1, so 2 1/4 kg.
Why others are wrong:
A โ Correct answer.
B โ This is the total amount of sugar used (1 1/4 kg), not the amount remaining after subtraction from the initial supply.
C โ This result occurs if only the first amount (3/4 kg) was subtracted from the initial amount (3 1/2 kg - 3/4 kg = 2 3/4 kg), ignoring the second usage.
D โ This result could occur from an error in finding the common denominator for the sum of used fractions (e.g., mistakenly calculating 3/4 + 1/2 = 2/3, then subtracting this from 3 1/2).
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