Any 2 digit number ending in 5 always ends in 25. Then multiply the tens digit by itself plus 1. 65 is 4225. 85 is 7225. and so on. This also works with bigger numbers but most people can't do that in their heads. I grew up without a calculator and know many short cuts.
Harvard University gives such simple problems for University entrants ? Further, students seeking admission into such reputed University definitely having sufficient knowledge. Such students need no spoon feeding. They need only hints and leave them to simplify to get the answer. This way they will have some thinking power which is most important for mathematics students.
I agree that these problems are designed to test critical thinking and problem-solving skills. Thanks for the insightful feedback! 👍Thanks for watching! I aim to provide clear explanations, and you’re right that students should be encouraged to think independently. 💡
At the end of the day , you have already used the multiplication and addition , So it is much simpler from the beginning to mutliply 81² by itself that is : 6561×6561 Using conventional method and then multiplying the result by 80 to get the final answer If you don't want to use a calculator! However; assuming there is no calculator available in our time , is like assuming that there is no food or water So the method shown here is meaningless and just waste of time
I appreciate you sharing your thoughts. It's interesting to consider the context of the interview situation.Thanks for the feedback! It's good to think about different approaches.💪💪💪
@luciakinska9742 Like several others in this series, the solution given is exactly what is not called for, a witless, turgid, working out of the whole thing. This guy doesn't get into Harvard. He gets told to go teach elementary or middle school kids. English literature or history maybe.
LOL, do you really want us to believe this is faster, simpler, and less prone to error than 81^2 x 81^2 x 80? edit i just did it my way and solved the problem, error free, in just over 6 minutes (Somebody rang the doorbell) edit: I do admit it was cute
Меня удивило, что даже 65^2 считается через квадрат суммы. Нельзя просто 65*65?? Скажите, пожалуйста, для каких учеников предлагается этот пример ( страна, возраст).
Because to multiply by 81 you have the choice: multiply by 3 four times, by 9 twice, or by 8 then by 10 and add once. Every operation mentioned above are easy.
81 by 81 is 6561, easy as 6400+80+81. You multiply by itself giving a number I call A, you multiply A by 81 giving a number I call B. And finally you substract B by A. Your need less than one minute and a poor knowledge is far enough.
simple way: 81^4(81-1)= 3.443.737.680....just 2 second
By calculator 😂😂😂😂
你說兩秒能解出來?....不用電子計算機情況下 我出一個類似題給你解 你2秒答出 我給你1萬台幣現金
81^4(81-1) 1秒
=81^4×80
=(81×81)^2×80
=6561^2×80 2秒
=6561x6561×80
=43046721×80
5秒
=34437377680
6秒
@@kennethkan3252 你光打出來都不只6秒 別說算
This is the correct way.🙏
Any 2 digit number ending in 5 always ends in 25. Then multiply the tens digit by itself plus 1. 65 is 4225. 85 is 7225. and so on. This also works with bigger numbers but most people can't do that in their heads. I grew up without a calculator and know many short cuts.
Why make things more difficult than necessary?
It's part of the process of new discoveries 💪💪💪👏👏👏
In Chinese ： 画蛇添足。 I simply did not see any new discoveries. In the process, more steps are introduced, thus more chances to make mistakes.
Just to make a video
Just no. Here there isn’t any cool idea that you could use later. Calculatîg 81^4 would ne easier than yr calcul@@superacademy247
真驚人 不管是用計算機的或不用計算機的都無語了 最震驚的是 無論用何種方式來驗算 都快過這
80x81^4
You don't need to know how to solve this to know that this is not the way to solve this.
Do you really think that's a better way to just calculate 81^4*80 directly?
81^5-81^4
=81*81*81*81*(81-1)
=(80+1)^2*(80+1)^2*80
=(6400+160+1)*(6400+160+1)*80
=6561*6561*80=3,443,737,680
80× 81⁴= , 1sec.
Very good
I'm glad you found the video helpful! 💯🙏🤩💕Thanks for your support! 🔥🔥✅💕
Harvard University gives such simple problems for University entrants ? Further, students seeking admission into such reputed University definitely having sufficient knowledge. Such students need no spoon feeding. They need only hints and leave them to simplify to get the answer. This way they will have some thinking power which is most important for mathematics students.
I agree that these problems are designed to test critical thinking and problem-solving skills. Thanks for the insightful feedback! 👍Thanks for watching! I aim to provide clear explanations, and you’re right that students should be encouraged to think independently. 💡
Well explain
NO!!
81^5=3^20, 81^4=3^16, 3^16(3^4-3^1) =3^16×80...
Вы что не умеете перемножать многозначные числа?
Queria entender a dificuldade de multiplicar 81×81×81×81×80
81^5-81^4
=81^4(81-1)
=81×81×81×81×80
=6561×6561×80
Good thing people invented the calculator ...
At the end of the day , you have already used the multiplication and addition ,
So it is much simpler from the beginning to mutliply 81² by itself that is :
6561×6561
Using conventional method and then multiplying the result by 80 to get the final answer
If you don't want to use a calculator!
However; assuming there is no calculator available in our time , is like assuming that there is no food or water
So the method shown here is meaningless and just waste of time
I appreciate you sharing your thoughts. It's interesting to consider the context of the interview situation.Thanks for the feedback! It's good to think about different approaches.💪💪💪
This is amazing method. Thank you ❤
You’re welcome 😊Glad you like it!💯🥰💕🙏😎Glad it was helpful!
@luciakinska9742
Like several others in this series, the solution given is exactly what is not called for, a witless, turgid, working out of the whole thing. This guy doesn't get into Harvard. He gets told to go teach elementary or middle school kids. English literature or history maybe.
@@superacademy247
It wasn't helpful at all. It is stupid.
Bài toán đến 81^4 ,80 = 2^5.3^8.5 là ok rồi
LOL, do you really want us to believe this is faster, simpler, and less prone to error than 81^2 x 81^2 x 80?
edit i just did it my way and solved the problem, error free, in just over 6 minutes (Somebody rang the doorbell)
edit: I do admit it was cute
The question is Harvard university?
Все делает для того что детей напугать, что бы они возненавидели математику.
Convoluted
Bài toán 81^5.81^4 = 80.81^4 =2^4.3^8.5 là ok rùi
What do you want to say?"
Меня удивило, что даже 65^2 считается через квадрат суммы. Нельзя просто 65*65??
Скажите, пожалуйста, для каких учеников предлагается этот пример ( страна, возраст).
Why losing so much time to calculate such an easy operation.
You'd better take care of the crying baby...
I think it's faster to calculate 81×81×81×81×81-81×81×81×81.
Because to multiply by 81 you have the choice: multiply by 3 four times, by 9 twice, or by 8 then by 10 and add once.
Every operation mentioned above are easy.
81 by 81 is 6561, easy as 6400+80+81. You multiply by itself giving a number I call A, you multiply A by 81 giving a number I call B.
And finally you substract B by A.
Your need less than one minute and a poor knowledge is far enough.
Or 6561x6561x80 And save 16.5 minutes of the video!
@@karencarpenter8275 Yes, that's the only good thing in this video.
@@karencarpenter827518.5 minutes 😂
This is a troll.....trying to get viewing hours. Look at the length of the video before watching.
Exactly
thats real long time wasting method. 81x81x81x81x80😅
North by North West.
Simply:
80×81
80×80=6400
+80=6480
That's certainly true -- and has nothing whatsoever to do with the problem given.
I guess we have one more data point on why the Romanovs fell.
6561
Tu uses du papier et de l encre
Seriously? Harvard university admission? Is this some kind of silly joke or it was for the admission in 1935?
Versteht überhaupt jemand akustisch, was der Sprecher sagt?
where's the trick? lol 20 min video. harvard gonna let you spend 20 mins on this question?
Nope. Even without calculator 2 mins max
這個問題我一看就是 81^4(81-1) 然後前面先組合...81*81 81*81 後面80保留就變成6561*6561*80=43046721*80=3443737680 應該說也只需2分鐘以內就能算出
數字太大了，天文數字
Are you crazy?
useles video. This has NOTHING to do with university!
Was soll das!
From the sequence 2 4 8 16 32 64 128 256 512 1024 2048 4096: 81^4=80^4+4*80^3+6*80^2+4*80+1=
40_960_000+
2_048_000+
38_400+
320+
1=
43_046_721
t = 60 , k = 100
? = [(t+5)k + (t+1)]^2 × 80 =
= [[(t+5)k]^2 + 2k(t+5)(t+1) + (t+1)^2]×80
= [ (t^2 + 10t + 25)k^2 +
+ 2k( t^2 + 6t + 5 ) +
+ ( t^2 + 2t + 1 ) ] × 80 =
= [ ( 3600+600+25)×10000 +
+ 200( 3600+360+5 ) +
+ ( 3600+120+1 ) ] × 80 =
= [ 42.250.000 +
793.000 +
3721 ] × 80 =
= 43.046.721 ] × 80 =
= 3.443.737.680
😊👍👋
81⁵ - 81⁴ = 80×81⁴
80×81⁴就這個數字很長而已....沒計算機大概需要1分鐘