need help!!!

sskl · 2005-04-01 20:27:42

Q1. Divide 64 into two parts so that the difference bettween 2/3 of one part and 1/4 of the other is equal to 28. What is the value of the larger part?

i hv did a little bit on tis qn... but i m stuck or isit i m wrong...
my working: let the larger no. be x.
let the smalelr no. be 64/x.
2/3x - 1/4(64/x) = 28
2/3x - 64/4x = 28
8x/12 - 192/12x = 28
i m stuck here...

Q2. A boy walks a certain distance at 9km/h. He finds that if he increases his speed by 1/3, he would have saved 4/3 hrs. Find the distance he walks.

for tis qn, i dun reli undertsand or know how 2 solve it... yarr...:|

MathsIsFun · 2005-04-01 22:48:52

Q1.

Full credit for having a go at it! You are using a good method, but I think the confusion is at the beginning. "Divide 64 into two parts" could mean "x times y equals 64" (as you thought of it), or "x plus y equals 64" (as in "let's divide this cake")

It works out neatly if you think of it as "x plus y equals 64"

So we can write it down as:

x+y=64
and
(2/3)x - (1/4)y = 28 (like you had it)

Let's solve:
x+y=64
y = 64-x
So: (2/3)x - (1/4)(64-x) = 28
then: (2/3+1/4)x - (1/4)64 = 28
(8/12+3/12)x - 16 = 28
(11/12)x=44
x= 44*12/11 = 4*12 = 48

Check it for me

MathsIsFun · 2005-04-01 23:10:26

Q2. A boy walks a certain distance at 9km/h. He finds that if he increases his speed by 1/3, he would have saved 4/3 hrs. Find the distance he walks.

I agree, it is hard to get your head around it.

Let's rephrase a little: 9km/h times (1+1/3) saves 4/3h, or an extra 3km/h saves 4/3h, so his time "t" is reduced.

OK, I think I can work this ... it has TWO things we don't know, time AND distance.

Let's call time "t" (in hours), and distance "x" (in km)

x = 9t (he went at 9km/h)
x = 9(1+1/3)(t-4/3) (increasing speed by 1/3 reduces time by 4/3)

Put the two together:

9t = 9(1+1/3)(t-4/3)
9t = 12(t-4/3)
9t = 12t-48/3
9t = 12t-16
-3t = -16
t = 16/3

Check this, too

sskl · 2005-04-04 21:55:44

gee... for question 1, i had checked and u are right! thank you... so my confusion is on the divide 64 into 2parts... thx alot!!:lol:
but for question 2, i have not check yet... sorry... i will try to find the time to check.... thx anyway...

Last edited by sskl (2005-04-04 21:56:29)

dannyk · 2005-04-05 07:30:06

I have forgotten how to find the square root of numbers by hand (without the use of a calculator), can anyone help me?
Thanks Dannyk

MathsIsFun · 2005-04-05 09:20:19

Example: Square Root of 2 (but works generally)

Guess: 1.5

2/1.5 = 1.333
Average the guess and the answer: (1.5+1.333)/2 = 1.417

Again:
2/1.417 = 1.411
Average the guess and the answer: (1.417+1.411)/2 = 1.414 DONE!

So, the more times you do this, the more accurate it becomes, but you can see that we have quickly arrived at three decimal places of accuracy. Stuff like this is called Successive Approximation.

Let's try another one. Square root of 10

Guess: 4
10/4=2.5
(4+2.5)/2 = 3.25
10/3.25=3.077
(3.25+3.077)/2 = 3.163
Test: 3.163*3.163 = 10.004 Amazing!

This can be useful if you are stuck without a calculator and need to find the diagonal of a square. I used it once for placing survey pegs in the ground when I was far from home.

classhelp · 2005-04-13 22:41:13

i dont know how to divide numbers without the use of calculators but am embarassed to ask infront of my class, for example 19.50 / 83. please help me.

Last edited by classhelp (2005-04-13 22:44:51)

MathsIsFun · 2005-04-13 22:55:16

Oh, you need a calculator for that !

Just kidding

19.5 / 83 would probably need long division. DECIMAL long division !

Looking at it, it would probably be easier written as 195/830 (it is the same, because I multiplied top AND bottom by the same number - 10)

MathsIsFun · 2005-04-13 23:00:53

So, we are asking how many 830s go into 195

It is going to be less than 1, so we need to put some extra decimal places:

830 ) 195.000

First step is to guess where to start. Largest multiple of 830 that isn't TOOO big. 2 x 830 = 1660, so 0.2 x 830 = 166 is a good starting point"

0.2
830 ) 195.000
166.000

Now we have see how much is left to go:

0.2
830 ) 195.000
166.000
29.000

So let's work on the 29: 3 x 830 = 2490:

0.23
830 ) 195.000
166.000
29.000
24.9
4.1

So let's work on the 4.1: 4 x 830 = 3320:

0.234
830 ) 195.000
166.000
29.000
24.9
4.10
3.32
0.78

Ohh, thats far enough !!

19.5 / 83 = 195/830 = 0.234

insomnia · 2005-04-13 23:02:30

Go on then

MathsIsFun · 2005-04-13 23:13:05

Did I get it right, insomnia?

I just type and type, and hope I get it right

insomnia · 2005-04-14 00:18:55

It's 0.235, rounded up. So, you were close

Zach · 2005-04-14 00:23:37

You sad person.

insomnia · 2005-04-14 00:24:12

You told me to do it!!!?

MathsIsFun · 2005-04-14 00:27:33

OK, good enough. So long as it wasn't the PM figuring the next Budget I'm safe.

Zach · 2005-04-14 00:31:21

They know budgets?

insomnia · 2005-04-14 00:33:42

Some of them do. only like 3 people. They are all like secretaries,etc. No-one important knows.

MathsIsFun · 2005-04-14 00:36:25

So they come here when the calcs get too hard.

Zach · 2005-04-14 00:37:58

Evil laughter?

insomnia · 2005-04-14 00:38:28

Yep. They use you. You think they are maths questions, but in fact you are deciding the budget for them. But, they can't read and get it wrong and screw up the country

E=tally=3 · 2005-04-14 03:17:03

budget people use this site!! wow!!! i am coming here all the time. i can talk tot hem about how this country is annoying, with its silly governments.

the prime minister here!! that is amazing! am a baffled that they come here... amazing!!!!!

Mr T · 2005-04-14 03:19:48

shut up

static helper · 2005-04-14 05:37:34

thats not nice BOOHOO. plz be nice. Or ill be mean to you

static helper · 2005-04-14 05:41:14

i was E=tally=3 last time, i didnt log in

Mr T · 2005-04-14 05:50:22

sorry, i didn't know. it is my job to be mean to guests so that they join to hurl abuse at me. xcessive maths nerd is an example of this

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