please help on this 7th grade question


Which choice has a value that is closest to the value of the following expression? 17/12 - 49/40


A. 1/4


B. 1/5


C. 1/6


D. 1/7

Respuesta :

Option B

The choice has a value that is closest to the value of the following expression 17/12 - 49/40 is [tex]\frac{1}{5}[/tex]

Solution:

Given that we have to find the value that is closest to the value of following expression

[tex]\frac{17}{12} - \frac{49}{40}[/tex]

Let us take L.C.M of denominators and solve the sum

L.C.M of 12 and 40

List all prime factors for each number

prime factorization of 12 = 2 x 2 x 3

prime factorization of 40 = 2 x 2 x 2 x 5

For each prime factor, find where it occurs most often as a factor and write it that many times in a new list.

The new superset list is

2, 2, 2, 3, 5

Multiply these factors together to find the LCM.

LCM = 2 x 2 x 2 x 3 x 5 = 120

Thus the given expression becomes:

[tex]\rightarrow \frac{17 \times 10}{12 \times 10} - \frac{49 \times 3}{40 \times 3}\\\\\rightarrow \frac{170}{120} - \frac{147}{120}\\\\\rightarrow \frac{170-147}{120}\\\\\rightarrow \frac{23}{120} = 0.1916 \approx 0.2[/tex]

[tex]0.2 = \frac{1}{5}[/tex]

Thus correct answer is option B

Answer:

B

Step-by-step explanation: