# Decimal Numbers Quiz Set 017

### Question 1

What is \${4.91^3 - 0.40^3}/{4.91^2 + 1.964 + 0.40^2}\$?

A

+4.51.

B

+5.31.

C

-5.31.

D

-4.51.

Soln.
Ans: a

We know \${a^3 - b^3}/{a^2 + ab + b^2}\$ is same as \${(a - b) × (a^2 + ab + b^2)}/{a^2 + ab + b^2}\$ which is same as a - b. So we get a - b = 4.91 - 0.40 = 4.51.

### Question 2

For what value of x would this expression be a perfect square: \$8.88 × 8.88 + x × 8.88 + 0.2 × 0.2\$?

A

0.4.

B

0.8.

C

0.2.

D

0.1.

Soln.
Ans: a

Comparing the given expression with \$a^2 + 2 × a ×b + b^2 = (a + b)^2\$, we see that if a = 8.88, and b = 0.2 then by inspection, x should be equal to 2b = 2 × 0.2 = 0.4.

### Question 3

What is \${48 × 6.7 - 67 × 8.5}/7.3\$?

A

\$-33{70/73}\$.

B

\$+33{70/73}\$.

C

\$-33{23/73}\$.

D

\$+33{23/73}\$.

Soln.
Ans: a

Observe that all fractional numbers are having one digit to the right of the dot. So we can cancel all the dots and get a plain expression: \${48 × 67 - 67 × 85}/73\$ which equals \${-2479/73}\$, which is same as: \$-33{70/73}\$

### Question 4

What is \$0.15966/0.02\$?

A

7.983.

B

6.983.

C

5.983.

D

8.983.

Soln.
Ans: a

The given expression can be written as \${15966/2} × {100/100000}\$ which is same as \${15966/2} × {1/1000}\$, which is same as \$7983 × {1/1000}\$, which is same as 7.983

### Question 5

What is \${31 × 8.8 - 27 × 3.2}/4.2\$?

A

\$44{8/21}\$.

B

\$44{5/21}\$.

C

\$44{1/21}\$.

D

\$44{11/21}\$.

Soln.
Ans: a

Observe that all fractional numbers are having one digit to the right of the dot. So we can cancel all the dots and get a plain expression: \${31 × 88 - 27 × 32}/42\$ which equals \${932/21}\$, which is same as: \$44{8/21}\$