Tag: maths

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Questions Related to maths

Multiple choice conversion of time time conversion time measurement of time maths

Which of these months does not have $31$ days?

  1. July

  2. March

  3. August

  4. November
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\Rightarrow$ All the 12 months have 31 or 30 days.

$\Rightarrow$  31 in case of January, March, May, July, august, October, December & 30 in case of April, June, September, November.
$\therefore$  $November$ does not have $31$ days.

Multiple choice conversion of time time conversion time measurement of time maths
At what time between  $1.30\mathrm { pm }$  and $2\mathrm { pm }$  will both the hands of a clock be at right angles?
  1. $4 \dfrac { 6 } { 11 }$
  2. $61 \dfrac { 5 } { 11 }$
  3. $\operatorname { Both } ( A ) \& ( B )$

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The angle between $2$ successive numbers in the clock is $\dfrac{360}{12}=30^{\circ}$

The angle between successive dots is $\dfrac{360}{60}=6^{\circ}$
For one rotation of minutes hand hours hand rotates by $30^{\circ}$
$\implies $ For increase in $1$ minute there is increase of $\dfrac{1}{2}^{\circ}$ for hours hand

At $1.50\text{pm}$
Angle Between hands of clock at $90+\dfrac{50}{2}=115$

For every $1$ min there is a decrease of $\dfrac{11}{2}^{\circ}$

For every $x$ min there is a decrease of $25^{\circ}$

$\implies x=\dfrac{25\times 2}{11}=4\dfrac{6}{11}$min

So at $4\dfrac{6}{11}$ pm the hands are perpendicular to each other.

Multiple choice conversion of time time conversion time measurement of time maths

If a clock strikes $12$ in $33$ seconds, it will strike $6$ in how many seconds?

  1. $\displaystyle \frac{33}{2}$
  2. $15$
  3. $12$
  4. $22$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In order to strike 12 there are 11 intervals of equal time = $\displaystyle \frac{33}{11}$ = 3 seconds each
Therefore to strike 6 it has 5 equal intervals, it requires 5 $\displaystyle \times $ 3 =15 sec.

Multiple choice conversion of time time conversion time measurement of time maths

A boat travels upstream from $B$ to $A$ and down stream from $A$ to $B$ in $3$ hours. If the speed of the boat in still water is $9\ km/hr$ and the speed of the current is $3\ km/ hr$, then the distance (in km) between $A$ and $B$ is

  1. $12$
  2. $8$
  3. $6$
  4. $4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the distance between $A$ and $B$ be $x$ km.
Upstream speed $= 9 - 2 = 6\ kmph$
Downstream speed $= 9 + 3 = 12\ kmph$
$\dfrac {x}{6} + \dfrac {x}{12} = 3\Rightarrow \dfrac {2x + x}{12} = 3\Rightarrow 3x = 36 \Rightarrow x = 12\ km$.

Multiple choice conversion of time time conversion time measurement of time maths

A mapping $f:N\rightarrow N$ where N is the set of natural numbers is defined as 
$ f\left( n \right) =\left{ { n }^{ 2 },for\quad n\quad odd\ 2n+1,for\quad n\quad even \right \$ .For $n\quad \Box \quad N$.Then f is

  1. Surjective but not injective

  2. Injective but not surjective

  3. Bijective

  4. Neither injective nor surjective
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As $f(3)=f(4)=9$
we can say that function is not one-one and $y=2$ does not exists.we can say that function is not onto. Therefore option D is correct.

Multiple choice conversion of time time conversion time measurement of time maths

A speed of $14$ metres per second is the same as:

  1. $28 \ \mathrm { km } / \mathrm { hr }$
  2. $46.6 \ \mathrm { km } / \mathrm { hr }$
  3. $ 50.4 \ \mathrm { km } / \mathrm { hr }$
  4. $ 70 \ \mathrm { km } / \mathrm { hr }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Speed\>=\>14\>\dfrac{m}{s}$

$=14\dfrac{\dfrac{1km}{1000}}{\dfrac{1hr}{3600}}$


$=\dfrac{14\cdot3600}{1000}\dfrac{km}{hr}=50.4\>\dfrac{km}{hr}$

Multiple choice conversion of time time conversion time measurement of time maths

What unit would you use to measure water?

  1. Hectare

  2. Litre

  3. Gram

  4. Metre
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hectare and metre are used to measure distances while gram is used to measure mass, and water is measured in terms of volume which is measured as litre.