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Answers
Required Answer:-
Question:
Design a class to print the sum of the following series.
S = 1 + 12 + 123 + .....1234567
Solution:
Here is the code. This is written in Java. It will calculate the sum of first 7 terms of the series.
public class SeriesSum {
public static void main(String[] args) {
int a=1,b=2,s=0;
for(int i=1;i<=7;i++)
{
s+=a;
a=a*10+b++;
}
System.out.println("Sum is: "+s);
}
}
Dry Run:
When i = 1:
a = 1
b = 2
s = 0 + 1 = 1
Now,
a = 1 × 10 + 2 = 12
b = 3
When i = 2:
a = 12
b = 3
s = 1 + 12
Now,
a = 12 × 10 + 3 = 123
b = 4
When i = 3:
a = 1234
b = 5
s = 1 + 12 + 123
Now,
a = 123 × 10 + 4 = 1234
b = 5
When i = 4:
a = 1234
b = 5
s = 1 + 12 + 123 + 1234
Now,
a = 1234 × 10 + 5 = 12345
b = 6
When i =5:
a = 12345
b = 6
s = 1 + 12 + 123 + 1234 + 12345
Now,
a = 12345 × 10 + 6 = 123456
b = 7
When i = 6:
a = 123456
b = 7
s = 1 + 12 + 123 + 1234 + 12345 + 123456
Now,
a = 123456 × 10 + 7 = 1234567
b = 8
When i = 7:
a = 1234567
b = 8
s = 1 + 12 + 123 + 1234 + 12345 + 123456 + 1234567
In this way, the program calculates the sum of the series.
Output is attached for verification.
