Solve 21/12+21/15-1/4

$$2 \frac { 1 } { 12 } + 2 \frac { 1 } { 15 } - \frac { 1 } { 4 }$$

Evaluate

$$\frac{39}{10}=3.9$$

Solution Steps

Multiply 2 and 12 to get 24.

$$\frac{24+1}{12}+\frac{2\times 15+1}{15}-\frac{1}{4}$$

Add 24 and 1 to get 25.

$$\frac{25}{12}+\frac{2\times 15+1}{15}-\frac{1}{4}$$

Multiply 2 and 15 to get 30.

$$\frac{25}{12}+\frac{30+1}{15}-\frac{1}{4}$$

Add 30 and 1 to get 31.

$$\frac{25}{12}+\frac{31}{15}-\frac{1}{4}$$

Least common multiple of 12 and 15 is 60. Convert \frac{25}{12} and \frac{31}{15} to fractions with denominator 60.

$$\frac{125}{60}+\frac{124}{60}-\frac{1}{4}$$

Since \frac{125}{60} and \frac{124}{60} have the same denominator, add them by adding their numerators.

$$\frac{125+124}{60}-\frac{1}{4}$$

Add 125 and 124 to get 249.

$$\frac{249}{60}-\frac{1}{4}$$

Reduce the fraction \frac{249}{60} to lowest terms by extracting and canceling out 3.

$$\frac{83}{20}-\frac{1}{4}$$

Least common multiple of 20 and 4 is 20. Convert \frac{83}{20} and \frac{1}{4} to fractions with denominator 20.

$$\frac{83}{20}-\frac{5}{20}$$

Since \frac{83}{20} and \frac{5}{20} have the same denominator, subtract them by subtracting their numerators.

$$\frac{83-5}{20}$$

Subtract 5 from 83 to get 78.

$$\frac{78}{20}$$

Reduce the fraction \frac{78}{20} to lowest terms by extracting and canceling out 2.

$$\frac{39}{10}$$

Factor

$$\frac{3 \cdot 13}{2 \cdot 5} = 3\frac{9}{10} = 3.9$$