Tag: calculations and mental strategies 1

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Questions Related to calculations and mental strategies 1

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.

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

After $12$ years I shall be $3$ times as old as I was $4$ years ago. Find my present age.

  1. $12$
  2. $13$
  3. $14$
  4. $15$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Let my present age$=x$ years

After $12$ years my age$=x+12$ years

$4$ years ago my age $=x-4$ years

According to the question,

$x+12=3\left(x-4\right)$

$\Rightarrow x+12=3x-12$

$\Rightarrow 3x-x=12+12$

$\Rightarrow 2x=24$ or $x=\dfrac{24}{2}=12$ years.

$\therefore$ my present age is $12$ years.
Multiple choice maths calculations and mental strategies 1 equations from statements forming equations from statements writing mathematical statements

The number of girls in a class is $5$ times the number of boys.Which of the following can be the total number of children in a class?

  1. $x+5y$
  2. $y-5x$
  3. $x-5y$
  4. $x+y=5$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Let the number of girls in a class be $x$

Number of boys be $y$

Given: Number of girls in a class is $5\times$ number of boys

$\therefore x=5y$ 

$\therefore$ total number of children$=x+5y$