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 5 of 6.
Satish reddy said:
1 decade ago
1397 is slightly less than 1400.
1397*1397 must be slightly less than 1400*1400 = 1960000.
There are only 2 numbers less than 1960000.
i.e [A] 1951609 ; [C]. 18362619.
[C] is too small. Hence the correct answer is (A).
1397*1397 must be slightly less than 1400*1400 = 1960000.
There are only 2 numbers less than 1960000.
i.e [A] 1951609 ; [C]. 18362619.
[C] is too small. Hence the correct answer is (A).
Rahul jadhav said:
1 decade ago
If you want to multiply this type of big no follow the step:
1397 * 1397 = ?
1397*1400 = 1955800.
and (1397+3 = 1400) So 1397*3 = 4191.
1955800-4191 = 1951609.
1397 * 1397 = ?
1397*1400 = 1955800.
and (1397+3 = 1400) So 1397*3 = 4191.
1955800-4191 = 1951609.
Jaishanth said:
8 years ago
@Kabita.
We should just minus the 3 from 1400 to make the formula=(a-b)^2.
1397=(1400-3).
We should just minus the 3 from 1400 to make the formula=(a-b)^2.
1397=(1400-3).
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.
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.
Esai said:
9 years ago
Explain me about digit sum method.
Naresh said:
9 years ago
@Thukki.
Digital sum means?
Digital sum means?
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.
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.
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