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If a and b are the tens digit and the units digit, respect
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21 Jul 2020, 09:07
21 Jul 2020, 09:07
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If a and b are the tens digit and the units digit, respectively, of the product \(325,189 \times 80,577\) what is the value of \(b-a\)?
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\(-2\)
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Re: If a and b are the tens digit and the units digit, respect
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21 Jul 2020, 09:18
21 Jul 2020, 09:18
2
We need to find the tens and units digit of \(325,189 \times 80,577\)
Now, if we need tens and units digit of any two numbers then we just need to consider the tens and units digit to get the answer
i.e. tens and units digit of \(325,189 \times 80,577\) will be same tens and units digit of \(89 \times 77\)
Now, we can multiple them directly and get the answer, but lets try a different approach
\(89 \times 77\) = \((90-1) \times (80-3)\)
= 90*(80-3) - 1*(80-3)
= 90*80 - 90*3 - 77
= 7200 - 270 - 77
= 6853
So, a = 5 and b = 3 and b-a = 3-5 = -2
So, Answer will be -2
Hope it helps!
Now, if we need tens and units digit of any two numbers then we just need to consider the tens and units digit to get the answer
i.e. tens and units digit of \(325,189 \times 80,577\) will be same tens and units digit of \(89 \times 77\)
Now, we can multiple them directly and get the answer, but lets try a different approach
\(89 \times 77\) = \((90-1) \times (80-3)\)
= 90*(80-3) - 1*(80-3)
= 90*80 - 90*3 - 77
= 7200 - 270 - 77
= 6853
So, a = 5 and b = 3 and b-a = 3-5 = -2
So, Answer will be -2
Hope it helps!
If a and b are the tens digit and the units digit, respect
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11 Mar 2021, 12:56
11 Mar 2021, 12:56
1
This is actually something where you can't use GRE calculator. By, solving this I actually learned a new thing. Let me share with you. Let's assume, we have two numbers, 1283 and 789.
1283 * 789 = 1012287 [multiply the both number]
283 * 789 = 223287 [multiply the first three digits of both number]
83 * 89 = 7387 [multiply the first two digits of both number]
3 * 9 = 27 [multiply the unit digits of both number]
Here, we multiply both numbers first, but when we take only three digits(from right to left), now the result of multiplication will be the same as the initial multiplication result only for the last three digits. The same thing happens for the last two digits and even for the unit digits too.
Now, we can easily solve this problem just by multiplying 89 and 77.
89 * 77 = 6853
So, a = 5, b = 3
b - a = 3 - 5 = -2 (Answer)
1283 * 789 = 1012287 [multiply the both number]
283 * 789 = 223287 [multiply the first three digits of both number]
83 * 89 = 7387 [multiply the first two digits of both number]
3 * 9 = 27 [multiply the unit digits of both number]
Here, we multiply both numbers first, but when we take only three digits(from right to left), now the result of multiplication will be the same as the initial multiplication result only for the last three digits. The same thing happens for the last two digits and even for the unit digits too.
Now, we can easily solve this problem just by multiplying 89 and 77.
89 * 77 = 6853
So, a = 5, b = 3
b - a = 3 - 5 = -2 (Answer)
