Tag: maths

Quizzes (518) Questions (9324)

Questions Related to maths

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, $43.09\times 23=991.07$.
Multiple choice maths decimal fraction multiplying decimals multiplication of decimals multiplication of division of decimal fraction by whole number and decimal fraction

(Three rupees $5$ paise) $\times$ (five rupees $40$ paise) is equal to

  1. $Rs. 18.90$
  2. $Rs. 16.47$
  3. $Rs. 17.64$
  4. $RS. 15.37$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

We know that 100 paise is nothing but 1 Rupee.

So $5Paise =  0.05 Rupees$
Also $40 Paise = 0.4 Rupees$
Now Three Rupees $5 Paise = 3 Rupees + 0.05 Rupees$
                                               $=3.05 Rupees$
Also Five Rupees $40 Paise= 5 Rupees + 0.40 Rupees$
                                              $= 5.40 Rupees$
Now to find $(Three\quad rupees\quad 5paise)×(fiverupees\quad 40paise)$
$3.05\times 5.40 = 16.47$

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

Using  identity the value obtained from the product $25.4 \times 24.6$ is

  1. $624.84$
  2. $642.84$
  3. $264.84$
  4. $62.84$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation


Given

$25.4\times24.6$

we can re-wright them as

$(25+0.4)\times (25-0.4)$

$\because \ we \ have \ an\ identity \ (a+b) (a-b)=a^2-b^2$

$a=25,\ b=0.4$


$= (25)^2-(0.4)^2$

$= 625- 0.16$

$=624.84$

$\therefore option\ A\ is\ correct.$


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

Without actual multiplication, the value $79.01 \times 79.01 + 2 \times 79.01 \times 20.99 + 20.99 \times 20.99$

  1. $10,009$
  2. $1000.06$
  3. $10,000$
  4. $1007$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$79.01\times 79.01+2\times 79.01\times 20.99+20.99\times 20.99....(1)$
$\dfrac {7901}{100}\times \dfrac {7901}{100}+2\times \dfrac {7901}{100}\times  \dfrac {2099}{100}+\dfrac {2099}{100}\times \dfrac {2099}{100}....(2)$

$7901\times 7901=(7901)^2 =(7900 +1)^2$    $\quad [\because \ 79^2=(80-1)^2\\ =80^2+1-2.80\\ =6400+1-160\\ =6241]$
$=(7900)^2 +1^2+2(7900)(1)$
$=62410000+1+15800$
$=62425801$ 

$2099\times 2099 =(2099)^2=(2100-1)^2$ $\quad [\because \ 21^2=(20+1)^2\\ =20^2+1+2.20\\ =400+40+1\\ =441]$
$=(2100)^2+1^2-2(2100)(1)$
$=4410000+1-4200$
$=4405801$

$7901\times 2099=(7900+1) (2100-1)$
$=(7900)(2100)-7900+2100-1$
$=16590000-7900+2100-1$
$=16584299\ =16584199$
from $(2)$
$\dfrac {62425801}{10000}+\dfrac {2\times 16584199}{10000}+\dfrac {4405801}{10000}$
$6242.5801+\dfrac {33168398}{10000}+440.5801$
$6242.5801+3316.8398+440.5801$
$=10,000$