The square root of 8 times the square root of 40=? Basic Algebra!
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- เผยแพร่เมื่อ 21 พ.ค. 2024
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Just saw that square root of 40 equals square root 5 x square root 8. Leaves you with square root 8 Times Square root 8 which equals 8 and then there is only square root of 5 left.
My solution also. 5 seconds in my head.
@@richardhole8429 I do enjoy the long form explanations. When I first started his video series I didn’t understand roots and powers but each lesson is stand alone and if you pay attention to one lesson you can easily start solving his other questions.
@@nicholasb8900 I am a retired engineer and math is nearly my "native language" so often I skip the explanations. Many complain about the detal in them. I taught both electronics na math and appreciate how he carefully explains the concepts. Advanced students can skip past what they don't need while beginners are well served. I like to see how many of the problems I can solve in my head.
@@rickholeelectrical/electronics engineer from Down Under. Totally agree and parallel lives ..
I also solved it in my head, but you did it more simply than I did! I did 8=4*2 and 40=4*10=4*2*5
I did a shorter method:
(Square Root of 8) x (Square Root of 8) x (Square Root of 5)
= (Square Root of 8) Squared x (Square Root of 5)
= 8 x (Square Root of 5)
mine was similar - but quickly saw that the problem could be rewritten as square root of (8 * 40) = square root (8 * 8 * 5) = 8 * square root (5)
If you re-write sqrt(8)*sqrt(40) as sqrt(8*8*5) it becomes obvious that d) is the correct answer: 8*sqrt(5).
I knew within seconds (without calculating the answer) that the correct answer was d. Since 40 factors into 8 X 5 there had to be a square root of 5 (or a multiple of 5) in the answer. The first 3 answers only had square roots of powers of 2. Only the last answer had a square root of 5 so it was the only one that could be correct.
Yeah I did this in my head:
sqrt(8) * sqrt(40) = sqrt(320) = sqrt(64*5) = sqrt(64) * sqrt(5) = 8 * sqrt(5) qed.
I said we have sqr root of 320. 320 is divisible by 64, which is useful...... 64 x 5 so it is 8 x 8 x5 so my answer is d
This makes my eyes start spinning round in my head. Maths was always like a foreign language to me.
I would do like this: 8x40 = 4x2 x 4x10 = 4x4 x 2x2x5 = 4² x 2² x 5 then V(4² x 2² x 5) = 8V5
Ahh the scenic route you take when you buy your first new car..
@@Johnwashere-dt2ov I know... it's because I am used to do the scenic route to show my math students all the lovely latches, levers and light switches of arithmetic.
@@panlomito what ever works that is all that matters
got it D reduce, multiply and reduce thanks for the fun
Got it. Brain exercise; no calculator needed. Thanks for previous lessons that made my solution easy.
Thank you!
I just removed two options that can't be right for obvious reasons, then I tried the 8✓5 one.
So ✓8✓40=✓320. I divided the 320 by 5 since that would give me 64 (=8²): ✓(5•8²)=✓5✓8²=8✓5.
Simpel. Divide square root 320 (coming from 8 x 40) by 5.
That leaves square root 64 x 5 which leads to 8x square root 5...
Took 15 seconds...
it just took me a few seconds and obviously it is d) 8 square root of 5.
now since 2,2 squared is the correct solution for 4,84 and 2,3 for 5,29 it is obvious that 2,2 times 8 , what results in 17,6 is correct, if you look now at the problem: root of 8 can't be 2,9 since squared it is 8,41. But it is 2,8 since it results squared in 7,84 and root of 40 is 6,3 because squared 39,69, as 6,4 squared is 40,96 so remains to multiply 2,8 and 6,3 what makes for 17,64.
So d) is the right answer.
The faster solution is though to see that 2,2 times 8 is 17,6 and from a) to c) there ain't a possibility since for example c) the root of 32 is smaller than 6 as 6 times 6 is 36 but 6 times 2 isn't even close to 17,6. And b) can't be, since the root of 32 is 5,6 / 4 = 1,4 but you see this on the spot and a ) is 5 times 2,8 = 14,0.
So that's it.
Le p'tit Daniel, now am I not a blue-eyed boy... ...Mama Christine ( from Providence ), you name it🐕🐕🐕🐕🐕
,
The correct answer is when you're not sure, always guess d.
Got it!
D I hope thank you
I got so close!
Answer is d)
✓8 x ✓40 = ✓8 x ✓(8 x 5) = 8✓5
D is guess
I came for the modern art
d) in about five seconds. Yeah, I'm tired.
d) 8 sq.root of 5
D is the only one that is simplified
Ans=√8×√40=√320=√64×√5=8√5.
I have question I know it’s dumb but I basically quit paying attention to math back in like 5th grade now I’m trying to join the military I have to score a 50 on the asvab the recruiter wants me to go to meps within the next 20 days is it possible to learn enough math to pass or is it crazy to even attempt it
I wish I would’ve payed attention but it’s too late for that I want a straightforward answer can I be taught basic algebra in 2 weeks or is it impossible
8√5
D)
The answer is d)
At 0:41 I got d)
I got D. 8×square root of 5
Genial
D
8 x sq rt of 5
d
LOL, you can tell at a glance that 8sqrt5 is correct because all the other choices can be reduced EDIT: And then it's easy to give a quick check: if 8 is outside that means 64 goes inside, and 64x5 = 320 which is the original problem anyway: sqrt(320).
Correct answer d
5square root 8
a
D calculators are for Rich people
RQ 8 X RQ 40 = ?
RQ 8 X RQ 8 X RQ 5 =
2 RQ 2 X 2 RQ 2 X RQ 5 = 4 RQ 4 X RQ5 =
4 X 2 X RQ 5 =
8 RQ 5, opção d)
Much bla bla about an overly complicated solution, because squareroot(8) times squareroot(8) times squareroot(5) is quite simple.
Did it in my head in about 20 seconds. Approximated the square roots and multiplied them, then looked for the closest answer. Easy.
That would work for multiple choice, but not if you have to figure out the answer yourself. Factoring out the 2's is the way to do it, and there are some variations of how to do that.
I did it in 19 seconds with my HP48 scientific calculator... I'm an engineer... Trained to get the right answer in the shortest time... Not be a math wizard...
@@anotherjoe5675 You said you did it in your head. Anyway, this wasn't a calculator problem. And a calculator would give you 17.8885, which isn't one of the choices. Yeah, you could get it from there by estimation, but I doubt you could do it in a couple of seconds. There were three other choices you would have to estimate before being confident of the answer.
But most importantly, this is a math lesson, and the objective is to understand a mathematical method, not whether you know how to use a calculator. As an engineer, you should appreciate that.
13.91
But first you have to learn how to clearly define the problem. Is the the square root of 8x? Or it is the square root of 8 times x times the sqare root of 40. In algebra X is usually the unknown quantity, so multiplcation is signified by a dot or *. Typical of youtube. Confusing question implying that if you don't understand the question, you are not as smart as the author.
😊😊😊😊
The question is clear.
× and • are standard symbols for multiplication in mathematical notation.
* is not. * is common in programming languages, but it's not a multiplication symbol in mathematical notation.
Also of course, even if the × was the letter x, we certainly aren't taking the square root of 8x because the × isn't under the radical sign.
Why in the name of God would you do it that way…just to make the video longer? C’mon man.
Not to be rude you re a teacher but too much information unnecessary very confusing 😖
8√5
D
8√5
D
D
Good night. I wanna sleep. Maths make me feel head ache