Step 6: Decimal Conversion (and back to fraction)
Convert each fraction to its decimal equivalent, add them, and then convert the sum back to a fraction.
21=0.5
31=0.333...
Add the decimals:
0.5+0.333...=0.8333...
To convert 0.8333... back to a fraction:
Let x=0.8333...
Multiply by 10: 10x=8.3333... (Equation 1)
Multiply by 100: 100x=83.3333... (Equation 2)
Subtract Equation 1 from Equation 2:
100x−10x=83.3333...−8.3333...
90x=75
x=9075
Simplify the fraction by dividing both numerator and denominator by their greatest common divisor, which is 15:
x=90÷1575÷15=65
The simplified answer is 65.
Step 7: Factoring out the Common Unit Fraction
First, find the least common multiple (LCM) of the denominators, which is 6. This means the common unit fraction is 61.
Express each fraction as a multiple of this common unit fraction:
21=63=3×61
31=62=2×61
Now, add these expressions by factoring out the common unit fraction 61:
3×61+2×61=(3+2)×61=5×61=65
The simplified answer is 65.
Step 8: Cross-Multiplication Method (Explicit Steps)
This method involves multiplying the numerator of each fraction by the denominator of the other fraction, adding these products, and placing the sum over the product of the denominators.
For 21+31:
Multiply the numerator of the first fraction (1) by the denominator of the second fraction (3): 1×3=3.
Multiply the numerator of the second fraction (1) by the denominator of the first fraction (2): 1×2=2.
Multiply the denominators together: 2×3=6.
Add the cross-products and place over the product of denominators:
2×3(1×3)+(1×2)=63+2=65
The simplified answer is 65.
Step 9: Area Model (Grid Method)
Imagine a rectangle divided into a grid where one dimension represents the first denominator and the other represents the second. For denominators 2 and 3, create a 2×3 grid, resulting in 6 small squares.
To represent 21, shade one row (or column) out of the two. If we shade one row of three squares, we shade 3 out of 6 squares.
To represent 31, shade one column (or row) out of the three. If we shade one column of two squares, we shade 2 out of 6 squares.
When combining these shaded areas, we have 3 squares from 21 and 2 squares from 31. In total, we have 3+2=5 shaded squares out of the 6 total squares in the grid.
Thus, the sum is 65.
The simplified answer is 65.
Step 10: Estimation and Verification
First