8TH GRADE MATH WORKSHEET 3 ANSWER

About "8th grade math worksheet 3 answer"  

8th grade math worksheet 3 answer :

Here we are going to see 10 practice questions of mixed topics. We have been preparing this set of questions in order to test how you understood the topics.

Practice questions of mixed topics in 8th grade math

Question 1 :

What fraction should be added with -4/9 to get 6/17 ?

(A)   104/163      (B)   136/151       (C)   122/153

Solution :

Let "x" be the required fraction

(-4/9) + x  =  6/17

Add both sides by 4/9

x  =  (6/17) + (4/9)  

  =  (54 + 68)/153

  =  122/153

Let us look into solution of next problem on "8th grade math worksheet 3 answer".

Question 2 :

Find for which value of x is the following equation true? 4^4x-7 = 4^{x - 1} .

(A) 2            (B) 3             (C) 4

Solution :

Since the base are same, we may equate the powers.

4x - 7  =  x - 1

Subtract both sides by x

4x - x - 7  =  -1

3x - 7  =  -1

Add both sides by 7

3x  =  -1 + 7

3x  =  6

Divide both sides by 3

x  =  6/3  =  2

Question 3 :

Express 412 x 10^-9 in standard form. 

(A) 41.2 x 10⁷       (B) 4.12 x 10^-7     (C) 4.12 x 10⁹

Solution :

412 x 10^-9  =  4.12 x 10² x 10^-9

  =  4.12 x 10^{(2 - 9)}

  =  4.12 x 10 ^-7

Question 4 :

Find the value of 5x - 6y - 8z if x = 2, y = 3 and z = -2.

(A) 5           (B) 8         (C) -18

Solution :

=  5x - 6y - 8z

=  5(2) - 6(3) - 8(-2)

=  10 - 18 + 16

=  26 - 18

=  8

Question 5 :

A number is 7 times greater than another number. If their sum is 96, find the numbers.

(A) 49, 51          (B) 84, 12         (C) 21, 75

Solution :

Let "x" and "7x" be two numbers 

x + 7x  =  96

8x  =  96

x  =  12

7x  = 7(12)  =  84

Hence the required numbers are 12 and 84.

Question 6 :

Which of the following are Pythagorean triplet?

(A) 12, 16, 20    (B) 9, 12, 15     (C) 10, 12, 34

Solution :

To prove the given numbers are in pythagorean triplet, we have to prove that the square of one term is equal to the sum of squares of the other numbers.

First let us take the numbers 12, 16, 20

20²  =  16² + 12²

400  =  256 + 144

400  =  400

Hence 12, 16, 20 are in pythagorean triplet.

Question 7 :

Which of the following is the cube of the even number?

(A) 343     (B) 729      (C) 1728

Solution :

Cube of a even number is also is even.

Hence 1728 is the cube of even number.

Question 8 :

Find the square root of 98464

(A) 272      (B) 242       (C) 212

Solution :

More examples please visit "Square root by long division method"

Hence the answer is 272.

Question 9 :

The sum of two numbers is 80 and their ratio is 3:5.Find the numbers.

(A) 30 and 50     (B) 18 and 30     (C) 21 and 35

Solution :

Let 3x and 5x be two numbers

3x + 5x  =  80

8x  =  80

x  =  80/8  =  10

3x  =  3(10)  =  30

5x  =  5(10)  =  50

Hence the required numbers are 30 and 50.

Question 10 :

Find the value of x ° if the lines AB and CD are parallel to each other

(A)   90°               (B)   123°            (C)   57°

Solution :

<AOB  =  360 - 246  =  114

<ACB  =  <AOB/2

  =  114/2

  =  57°

Hence the required angle is 57°.

Answers:

(1)  122/153

(2)  2

(3)   4.12 x 10^-7

(4)  8

(5)  12 and 84

(6)  12, 16, 20

(7)  1728

(8)  272

(9)  30 and 50

(10)  57

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