Tag: multiplying decimals

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Questions Related to multiplying decimals

Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

The value of $\dfrac{0.008\times 0.01\times 0.0072}{(0.12\times 0.0004)}$ is:

  1. $0.012$
  2. $0.12$
  3. $1.02$
  4. $1.2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given expression 


$\dfrac{0.008\times 0.01\times 0.0072}{(0.12\times 0.0004)}$ 

$=\dfrac {0.008\times0.01\times0.0072}{0.000048}$

$=0.00008\times\dfrac{0.0072}{0.000048}$

$=\dfrac{8}{48}\times\dfrac{72}{1000}$

$=0.012$

Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

Number of zero's in the product of
$5 \times 10 \times 25 \times 40 \times 50 \times 55 \times 65 \times 125 \times 80 $

  1. $8$
  2. $9$
  3. $12$
  4. $13$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$5 \times 10 \times 25 \times 40 \times 50 \times 55 \times 65 \times 125 \times 80 $
$= 5 \times 2 \times 5 \times 5^2 \times 2^3 \times 5 \times 2 \times 5^2 \times 11 \times 5 \times 13 \times 5 \times 5^3 \times 2^4 \times 5$
$= 2^9 \times 5^{13}\times 11 \times 13 = (2 \times 5)^9 \times 5^4 \times 11 \times 13$


As we know that zeroes are formed by the product of a $2$ and a $5$ i.e. $2$ x $5$. 

Therefore, number of zeroes depends on the number of pairs of $2$'s and $5$'s that can be formed in the given product. 

Since $9$ pairs of $2$'s and $5$'s are formed in the given product, hence there will be $9$ zeroes in the given product.

Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

If u, v and w are the digits of decimal system, then the rational number represented by 0.uwuvuvuvuv......is

  1. (100 uw + 99 uv)/99

  2. (99uw + uv)/980

  3. (99uw + uv)/9900

  4. (9uw + 99uv)/900
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

x =0.uwuvuvuvuv...
x = O.uwuv
(i) x 100
100x = uw. uv
(ii) x 100
10000x = uwuv - uv
(iii) - (ii)

Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

Each piece of cardboard is $0.3\ cm$ thick. If Marie stacks $8$ pieces of cardboard on top of one another, how thick will the stack be?

  1. $2.4\ cm$
  2. $24\ cm$
  3. $2.1\ cm$
  4. $21\ cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

It is given that each piece of cardboard is $0.3$ cm thick which means that one piece is $0.3$ cm thick.


If Marie stacks $8$ pieces of cardboard, then the thickness of $8$ pieces of cardboard will be:

$0.3\times 8=2.4$ cm

Hence, the stack will be $2.4$ cm thick.

Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

If $100\times \text{ ? }=352$. Then, find the missing number.

  1. $0.352$
  2. $352$
  3. $35.2$
  4. $3.52$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let $x$ be the missing number.


$100\times x=352\ \Rightarrow 100x=352\ \Rightarrow x=\dfrac { 352 }{ 100 } \ \Rightarrow x=352\times 0.01\quad \quad \quad \quad \quad \left{ \because \quad \dfrac { 1 }{ 10 } =0.1,\dfrac { 1 }{ 100 } =0.01,.... \right} \ \Rightarrow x=3.52$

Hence, the missing number is $3.52$.

Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

Calculate $456.78\times 8$.

  1. $36542.4$
  2. $365.424$
  3. $3,654.24$
  4. $36.5424$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Let us first multiply the two given numbers $456.78$ and $8$ without decimal point:

$45678\times 8=365424$

Since, $456.78$ has two decimal places, therefore the answer $365424$ should also have two decimal places that is $3654.24$.

Hence, $456.78\times 8=3,654.24$.
Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

$45.678\times \text{ ? }=1187.628$. Find $?$.

  1. $26$
  2. $27$
  3. $28$
  4. $29$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let $x$ be the missing number.


$45.678\times x=1187.628\ \Rightarrow 45.678x=1187.628\ \Rightarrow \dfrac { 45678x }{ 1000 } =\dfrac { 1187628 }{ 1000 } \quad \quad \quad \quad \quad \left{ \because \quad \dfrac { 1 }{ 10 } =0.1,\dfrac { 1 }{ 100 } =0.01,.... \right} \ \Rightarrow x=\dfrac { 1187628 }{ 1000 } \times \dfrac { 1000 }{ 45678 } \ \Rightarrow x=26$

Hence, the missing number is $26$.

Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

Multiply $43.09$ with $23$.

  1. $99.107$
  2. $991.07$
  3. $9910.7$
  4. $9.9107$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Let us first multiply the two given numbers $43.09$ and $23$ without decimal point:
$4309\times 23=99107$
Since, $43.09$ has two decimal places, therefore the answer $99107$ should also have two decimal places that is $991.07$.
Hence, $43.09\times 23=991.07$.