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 3 of 6.
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?
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.
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.
Rinki said:
9 years ago
Easy explanation. Thank you all.
Baskar said:
9 years ago
Can you explain logic @Prashant.
Nagarjuna goud said:
9 years ago
Hi @Sravani.
I did not understand your answer how it came?
I did not understand your answer how it came?
Sindu said:
8 years ago
1397*1397= (1397*1000)+(1397*400)-(1397*3) = 1951609.
Split 1397 as (1000+400-3).
Split 1397 as (1000+400-3).
Kabita said:
8 years ago
@Sindu.
Please tell me How 3 came?
Please tell me How 3 came?
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).
Pratheev Kalyan said:
8 years ago
1397*1397=?
Since 1400*1400=1960000, so the result must be less than 1960000. By this, options c and d gets eliminated. Remaining is a and b.
The number 1397 is divisible by 11. So, the answer must also be divisible by 11. Thus option b(not divisible by 11) is eliminated and option a is the answer.
Since 1400*1400=1960000, so the result must be less than 1960000. By this, options c and d gets eliminated. Remaining is a and b.
The number 1397 is divisible by 11. So, the answer must also be divisible by 11. Thus option b(not divisible by 11) is eliminated and option a is the answer.
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