Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 5)
5.
1397 x 1397 = ?
Answer: Option
Explanation:
| 1397 x 1397 | = (1397)2 |
| = (1400 - 3)2 | |
| = (1400)2 + (3)2 - (2 x 1400 x 3) | |
| = 1960000 + 9 - 8400 | |
| = 1960009 - 8400 | |
| = 1951609. |
Discussion:
55 comments Page 4 of 6.
Baskar said:
9 years ago
Can you explain logic @Prashant.
Rinki said:
9 years ago
Easy explanation. Thank you all.
Smile said:
9 years ago
@Thukki.
What is digital sum how we get num 4 above.
What is digital sum how we get num 4 above.
Vikas pathak said:
9 years ago
We have options,
So try to find the nearest answer available in the options.
If we round off 1397 we get 1400,
Just do the square of 14 and, it comes to 196.
Check the nearest answer available to figure 196 (Check the first three digit).
The 1st 3 digit of the nearest answer should be less from 196 as we have to deduct 3 from 1397.
So try to find the nearest answer available in the options.
If we round off 1397 we get 1400,
Just do the square of 14 and, it comes to 196.
Check the nearest answer available to figure 196 (Check the first three digit).
The 1st 3 digit of the nearest answer should be less from 196 as we have to deduct 3 from 1397.
Surya said:
9 years ago
Hello, @Thukki.
Thank you for sharing about Digital Sum method. What if the option has another number which also have 4 as Digital Sum. Will this work foe all the problems?
Thank you for sharing about Digital Sum method. What if the option has another number which also have 4 as Digital Sum. Will this work foe all the problems?
Gore said:
9 years ago
@Tamil.
Your answer is perfect.
Your answer is perfect.
Naresh said:
9 years ago
@Thukki.
Digital sum means?
Digital sum means?
Esai said:
9 years ago
Explain me about digit sum method.
Thukki said:
9 years ago
In shortcut method:
Digital sum (D. S) method i.e 4.
D.S of 1397 is 2, so 1397*1397 is 2*2 = 4.
Now out of all the options, the D.S of option a is 4.
Digital sum (D. S) method i.e 4.
D.S of 1397 is 2, so 1397*1397 is 2*2 = 4.
Now out of all the options, the D.S of option a is 4.
Prashant said:
1 decade ago
Shortcut: Digital sum (D. S) method i.e 4.
D.S of 1397 is 2, so 1397*1397 is 2*2 = 4.
Now out of all the options the D.S of option a is 4.
D.S of 1397 is 2, so 1397*1397 is 2*2 = 4.
Now out of all the options the D.S of option a is 4.
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