Question

iii. 72% of 25 students are good in mathematics. How many are not good in mathematics?

Answer 1

Solution -

It is given that 72% of 25 students are good In mathematics.

We have to find how many of them are not good in mathematics.

Suppose we consider a hypothetical situation where there are only two cases .

(a). The student is good in mathematics.

(b). The student isn't good in mathematics.

If a student is counted as good in mathematics , it means he isn't good.

So

Number of students " good in mathematics "

>> 72% of 25

>> 72/100 × 25

>> 72/4

>> 13

So, number of students " not good in mathematics "

>> 25 - 13

>> 12

Answer - There are 12 students who are not good in mathematics.

______________________________________

Answer 2

$\huge \fcolorbox{red}{brown}{ \bf \color{yellow}{7 \: students}}$

Step-by-step explanation:

QUESTION :-

72% of 25 students are good in mathematics. How many are not good in mathematics?

____________________

SOLUTION :-

A.T.Q.,

72% of 25 students are good in mathematics.

To find,

How many of them are not good in mathematics.

In such case,

There are only two results for these 25 students :-

1. A student is good in mathematics.
2. Or, A student isn't good in mathematics.

We can solve it in two ways,

____________________

WAY 1 :-

Because 72% of 25 students are good in mathematics.

So,

Let's find (in numbers) how many are good in mathematics.

Students no. (good in mathematics)

$= \bf72\% \: of \: 25 \\ \\ \bf = \frac{ \cancel{72} {}^{18} }{ \cancel{100}_{ \cancel4}} \times \cancel{ 25} \\ \\ \large\bf = \blue{\underline{ \red{18}}}$

Hence,

18 students are good in mathematics.

$\:$

Now,

Because there can be only two results. So,

Total possible results = result (1) + result (2)

= result (2) = possible results - result (1)

=> Students not good in mathematics

= Total students – students good in students

= 25 - 18

= 7

$\:$

Hence,

7 Students are not good in mathematics.

____________________

WAY 2 :-

As given that,

72% of 25 are good in mathematics.

Then,

28% are not in mathematics.

Because, As mentioned above,

There can be only two results.

So,

Possible results = result (1) + result (2)

= result (2) = possible results - result (1)

=> students not good in mathematics (in %)

= total students (in %) – students good in mathematics (in %)

= 100% - 72%

= 28%

So,

28% of 25 students are not good in mathematics

$\bf = 28\% \: of \: 25 \\ \\ \bf = \frac{ \cancel {28}^{ \red 7} }{ \cancel{100}_{ \cancel{4}}} \times \cancel{25}$

Hence,

7 students are not good in mathematics.

____________________

Hope it helps.

#BeBrainly :-)