# Decimal Numbers Quiz Set 018

### Question 1

What is y in \$4.121 + 0.4 + y = 0.09\$?

A

-4.431.

B

+4.431.

C

+4.134.

D

-4.134.

Soln.
Ans: a

y = 0.09 - (0.4 + 4.121) = -4.431.

### Question 2

What is \${94 × 9.8 - 73 × 8.9}/8.2\$?

A

\$33{9/82}\$.

B

\$33{7/82}\$.

C

\$33{5/82}\$.

D

\$33{11/82}\$.

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: \${94 × 98 - 73 × 89}/82\$ which equals \${2715/82}\$, which is same as: \$33{9/82}\$

### Question 3

What is x in \${149/0.0149} = {1.49/x}\$?

A

\$1.49 × 10^{-4}\$.

B

\$1.49 × 10^{-5}\$.

C

\$1.49 × 10^{-3}\$.

D

\$1.49 × 10^{-2}\$.

Soln.
Ans: a
Transposing, x = \$1.49 × {0.0149/149}\$ which gives 0.000149, which, in scientific form is \$1.49 × 10^{-4}\$.

### Question 4

What is \${7.91^3 - 0.50^3}/{7.91^2 + 3.955 + 0.50^2}\$?

A

+7.41.

B

-7.41.

C

+8.41.

D

-8.41.

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 = 7.91 - 0.50 = 7.41.

### Question 5

What is \${0.70 × 0.70 × 0.70 + 0.03 × 0.03 × 0.03}/{3.50 × 3.50 × 3.50 + 0.15 × 0.15 × 0.15}\$?

A

\$1/5^3\$.

B

\$1/7^3\$.

C

\$1/5^2\$.

D

\$1/7^2\$.

Soln.
Ans: a

By inspection, the given ratio is same as \${0.70 × 0.70 × 0.70 + 0.03 × 0.03 × 0.03}/{5^3 × ({0.70 × 0.70 × 0.70 + 0.03 × 0.03 × 0.03})}\$ which is \$1/5^3\$. 