Aptitude - Percentage - Discussion
Discussion Forum : Percentage - General Questions (Q.No. 7)
7.
In a certain school, 20% of students are below 8 years of age. The number of students above 8 years of age is 
of the number of students of 8 years of age which is 48. What is the total number of students in the school?
Answer: Option
Explanation:
Let the number of students be x. Then,
Number of students above 8 years of age = (100 - 20)% of x = 80% of x.
 80% of x = 48 + |
2 | of 48 |
| 3 |
 |
80 | x = 80 |
| 100 |
x = 100.
Video Explanation: https://youtu.be/yPfocU6DA2M
Discussion:
135 comments Page 7 of 14.
Rumman said:
1 decade ago
LET TOTAL STUDENT BE X.
THEN STUDENT BELOW AGE 8=20% OF X=20/100 OF X.
STUDENT EXACTLY AT 8 = 48.
STUDENT ABOVE 8 = 2/3 OF 48 = 32.
20X/100+48+32 = X;
20X+4800+3200 = 100X;
80X = 8000;
X = 100;
SIMPLE.
THEN STUDENT BELOW AGE 8=20% OF X=20/100 OF X.
STUDENT EXACTLY AT 8 = 48.
STUDENT ABOVE 8 = 2/3 OF 48 = 32.
20X/100+48+32 = X;
20X+4800+3200 = 100X;
80X = 8000;
X = 100;
SIMPLE.
Naresh said:
1 decade ago
Can you explain me when should we take 100-20 in the above given problem and then whats the need to consider it for 100%?
Saif Alam said:
1 decade ago
Let total student = x.
Below 8 year = 20% of x i.e x/5.
Exact 8 year = 48.
Above 8 year = 2/3*48=32.
So,
Total student = x/5 + 48 + 32.
x = x/5 + 80.
x-x/5 = 80.
4x = 400.
x = 100.
Below 8 year = 20% of x i.e x/5.
Exact 8 year = 48.
Above 8 year = 2/3*48=32.
So,
Total student = x/5 + 48 + 32.
x = x/5 + 80.
x-x/5 = 80.
4x = 400.
x = 100.
Debasmita said:
1 decade ago
Answer should be 150.
Explanation:
Let, x = no. of student at 8 years old.
Above 8 years old = 2/3 of x.
=> x = 48*(3/2) = 72.
Students above 8 years and 8 years old = 72+48 = 120.
If (100-20)% = 80% equals 120 students.
1% equals 120/80.
100% equals (120/80)*100 = 150.
Explanation:
Let, x = no. of student at 8 years old.
Above 8 years old = 2/3 of x.
=> x = 48*(3/2) = 72.
Students above 8 years and 8 years old = 72+48 = 120.
If (100-20)% = 80% equals 120 students.
1% equals 120/80.
100% equals (120/80)*100 = 150.
Mahi said:
1 decade ago
How came 2/3?
Shrihari said:
1 decade ago
Hi answer is 100.
Here they mentioned above 8 year old students are 2/3 of 48 of age 8.
So 2/3 of 48 = 32.
So 32+48 = 80.
Now we left with 20% of students which are below 8.
There will be maximum 100% so they asking 20%.
We already found 80% of the students strength i.e. 80.
So 20% of 100 is 20. So 80(8 year+above 8 year) + 20(less than 8) = 100.
Hope you guys got it.
Here they mentioned above 8 year old students are 2/3 of 48 of age 8.
So 2/3 of 48 = 32.
So 32+48 = 80.
Now we left with 20% of students which are below 8.
There will be maximum 100% so they asking 20%.
We already found 80% of the students strength i.e. 80.
So 20% of 100 is 20. So 80(8 year+above 8 year) + 20(less than 8) = 100.
Hope you guys got it.
Nidhi said:
1 decade ago
Let the total students be x.
20%of x = No of students below age 8.
48 = No of students of age exact 8. Given.
No of students above age 8 is 2/3 of no of students of age exact 8.
That is 2/3 of 48 = 32.
So above 8 is 32.
Exact 8 is 48x. Total of above is 80.
Now students below age 8 is 20% of total.
Therefore 20/100 of x = (x-80).
20x = 100x-8000.
8000 = 80x.
x = 100.
Therefore answer is 100.
20%of x = No of students below age 8.
48 = No of students of age exact 8. Given.
No of students above age 8 is 2/3 of no of students of age exact 8.
That is 2/3 of 48 = 32.
So above 8 is 32.
Exact 8 is 48x. Total of above is 80.
Now students below age 8 is 20% of total.
Therefore 20/100 of x = (x-80).
20x = 100x-8000.
8000 = 80x.
x = 100.
Therefore answer is 100.
Narendra umraiya said:
1 decade ago
By 100% concept:
20% students is = remaining (exactly 8 yrs and above 8 yrs).
Below 8yrs i.e. 100%-20% = 80%.
80% = 48+2/3*48--equation 1 (48 is exactly 8 yrs and 2/3*48 is above 8 years a/c to question).
By equation 1 80% = 48+2/3*48 = 80.
100% = ? (100% means total students).
By cross multiply we get 100 answer.
20% students is = remaining (exactly 8 yrs and above 8 yrs).
Below 8yrs i.e. 100%-20% = 80%.
80% = 48+2/3*48--equation 1 (48 is exactly 8 yrs and 2/3*48 is above 8 years a/c to question).
By equation 1 80% = 48+2/3*48 = 80.
100% = ? (100% means total students).
By cross multiply we get 100 answer.
Gautam said:
10 years ago
No of students of age 8 is 48.
Given no of students above 8 = 2/3 of 48 = 32.
20 % are below 8 age.
Therefore 80 % are equal or above 8.
Therefore 80 % of x = 80 (32 + 42).
So x = 100.
Given no of students above 8 = 2/3 of 48 = 32.
20 % are below 8 age.
Therefore 80 % are equal or above 8.
Therefore 80 % of x = 80 (32 + 42).
So x = 100.
Robbin said:
10 years ago
Why 2/3?
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