Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 118)
118.
The sum of all two digit numbers divisible by 5 is:
Answer: Option
Explanation:
Required numbers are 10, 15, 20, 25, ..., 95
This is an A.P. in which a = 10, d = 5 and l = 95.
tn = 95 
a + (n - 1)d = 95
10 + (n - 1) x 5 = 95
(n - 1) x 5 = 85
(n - 1) = 17
n = 18
 Requuired Sum = |
n | (a + l) | = | 18 | x (10 + 95) = (9 x 105) = 945. |
| 2 | 2 |
Discussion:
8 comments Page 1 of 1.
Deepa said:
2 years ago
Could anyone explain it easily, please?
Rushiesh said:
3 years ago
@Barath.
How -5 came? Explain please.
How -5 came? Explain please.
(1)
Barath said:
4 years ago
10,15,20,25,....,95 and also add 5 infront of 10.
then,
5,10,15,...95.
=(5(1+2+3+...+19))-5.
Formula for (1+2+3+...+19) is;
n(n+1)/2.
= (5(19(20)/2))-5.
= 950 - 5.
= 945.
then,
5,10,15,...95.
=(5(1+2+3+...+19))-5.
Formula for (1+2+3+...+19) is;
n(n+1)/2.
= (5(19(20)/2))-5.
= 950 - 5.
= 945.
Janardhan jada said:
4 years ago
Please explain in simple method.
Parul said:
7 years ago
= (5*1)+(5*2)+(5*3)+.....(5*19).
= 5(1+2+3+......19).
= 5* 19* (19+1)/2.
= 5* 19* 20/2.
= 5*19*10.
= 950.
= 5(1+2+3+......19).
= 5* 19* (19+1)/2.
= 5* 19* 20/2.
= 5*19*10.
= 950.
Zunaira Zafar said:
7 years ago
What is meant by "l" here and we take "10" as the value of a? What does a denote? Please explain.
Nasir said:
8 years ago
99-10+1/5=18,
So,we can easily find option D (9+4+5=18).
So,we can easily find option D (9+4+5=18).
Ajax said:
1 decade ago
Finding n shortcut is = 99-10+1 /5 =18.
And find sum of 18 numbers.
And find sum of 18 numbers.
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