Tag: maths

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Questions Related to maths

Multiple choice maths calculations and mental strategies 1 equations from statements forming equations from statements writing mathematical statements

If a number, when divided by $4$, is reduced by $21$, the number is:

  1. $18$
  2. $20$
  3. $28$
  4. $38$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Let $x$ be the number.
If a number is divided by the $4$ the expression becomes $\dfrac{x}{4}$
If a number, when divided by $4$, is reduced by $21$, then the equation is
$\dfrac{x}{4}=x-21$
$\Rightarrow\,\dfrac{x}{4}-x=-21$
$\Rightarrow\,\dfrac{x-4x}{4}=-21$
$\Rightarrow\,-3x=-21\times 4$
$\Rightarrow\,x=\dfrac{21}{3}\times 4=7\times 4=28$
$\therefore\,$,the number is $28$
Multiple choice maths calculations and mental strategies 1 equations from statements forming equations from statements writing mathematical statements

The product of two numbers is 1296. If one number is 16 times the other, then the two numbers are 

  1. 144, 25

  2. 81, 49

  3. 144, 9

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the first number be $x$. Then, other number is $16x$.


Now, $x \times 16x =1296$

$16x^2=1296$
$x^2=81$
$x=9$
$16x=16\times 9=144$

Thus, the two numbers are $9$ and $144.$

Multiple choice maths calculations and mental strategies 1 equations from statements forming equations from statements writing mathematical statements

The average age of the mother and her six children is 12 years which is reduced by 5 years if the age of mother is excluded. How old is the mother?

  1. 40 years

  2. 42 years

  3. 48 years

  4. 50 years
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The average age of the mother and her 6 children (7 people total) is 12 years, meaning their total age is 7 * 12 = 84 years. When the mother is excluded, the average of the 6 children drops by 5 years to 12 - 5 = 7 years, making the total age of the children 6 * 7 = 42 years. Subtracting the children's total age from the family's total age gives the mother's age as 84 - 42 = 42 years.

Multiple choice maths calculations and mental strategies 1 equations from statements forming equations from statements writing mathematical statements

Two years ago, a father was five times as old as his son. Two years later, father age will be 8 more than three times the age of the son. Find the sum of present ages of father and son.

  1. 62 years

  2. 52 years

  3. 42 years

  4. 34 years
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let F and S be the present ages of the father and son. Two years ago, F - 2 = 5(S - 2), which simplifies to F - 5S = -8. Two years later, F + 2 = 3(S + 2) + 8, which simplifies to F - 3S = 12. Solving these simultaneous equations gives S = 10 and F = 42, so the sum of their present ages is 42 + 10 = 52 years.

Multiple choice maths calculations and mental strategies 1 equations from statements forming equations from statements writing mathematical statements

If $50$ is subtracted from two-third of a number, the result is equal to sum of $40$ and one-fourth of that number. What is the number? 

  1. $174$
  2. $216$
  3. $246$
  4. $336$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let the number be N. According to the problem, (2/3)N - 50 = 40 + (1/4)N. Rearranging terms gives (2/3)N - (1/4)N = 90. Finding a common denominator results in (5/12)N = 90, which means N = 90 * 12 / 5 = 216.

Multiple choice maths calculations and mental strategies 1 equations from statements forming equations from statements writing mathematical statements

The average of 9  consecutive numbers with difference of 9 is 79 , then with smallest number  among them ?

  1. 43

  2. 34

  3. 52

  4. 44
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For 9 numbers with difference 9, the average is the middle number (the 5th number). So 5th number = 79. The sequence is 79-4*9, 79-3*9, 79-2*9, 79-9, 79, 79+9, ... Smallest = 79 - 36 = 43.