Math Is Fun Forum

jmoore

Member

Registered: 2008-01-09

Posts: 25

How to work this out not sure?

"How Many pieces of string each measuring 1.5m, can be cut from a ball which is 90m long?"

now i thought about saying to myself if it was 1m it would be 90 now since they want a meter and a half find half of 90 which 45 and take that away from 90 would that leave you with the answer?

Question 2

"a set male in a resturant is £5.60. if senior citizens are given 5% reduction, what would the bill amount to if 10 senior citizens had such a meal" 

this is what i had since there is 10 of them the bill would be 560 and the percent would be 50% so 50% of 560 is 280 so the bill would be £280, am i correct in thinking this

thanks

Joe

Last edited by jmoore (2008-03-24 01:05:31)

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: How to work this out not sure?

#1.
It looks like you have difficulty understanding the question. Let me explain it this way.

You have a piece of string that is 90 metres long. Cut off 1.5 metres from it. So you have a 1.5-metre length of string and the first piece of string is now 88.5 metres long.

Cut off another 1.5 metres from the first piece of string. What do you have? Now you have two 1.5-metre-length strings and the first piece of string is 87 metres long.

Cut off another 1.5 metres again. Now you have three 1.5-metre-length strings and the first piece of string becomes 85.5 metres long.

The question is: If you keep cutting off 1.5 metres from the piece of string until you cannot cut off any more, how many times can you do that? In other words, how many 1.5-metre-length strings are you going to end up with?

#2
What is 5% of £5.60?

0.05 × £5.60 = £0.28

So take £0.28 away from £5.60. £5.60 − £0.28 = £5.52. That’s the cost of a meal for a senior citizen – £5.52. Hence the cost of 10 such meals will be …? How much?

Last edited by JaneFairfax (2008-03-25 01:37:25)

jmoore

Member

Registered: 2008-01-09

Posts: 25

Re: How to work this out not sure?

Ok so with this one

"A Box of decorations which cost £30 last xmas is reduced in price by 12% what is the revised price?"

what i did was 12x30 which is 90/100 0.09 took that away and i got £21 is that correct

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

Re: How to work this out not sure?

No. You need to take 12% of 30 and subtract that from 30.

12% of 30 = 30 x 0.12 = 3.6

30 - 3.6 = 26.4

£26.40 is your new price.

jmoore

Member

Registered: 2008-01-09

Posts: 25

Re: How to work this out not sure?

thanks can i ask how do you take decimal numbers like 3.6 away from whole numbers like 30 i can't seem to do it? how do you got about setting the numbers up like when you do taking away i would do this

  10
- 20
-------

-------

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

Re: How to work this out not sure?

hmm this is just basic arithmetic. Im not sure the explanation im going to give you is the best out there but lets say you want to take away 3.6 from 30. Maybe it would be easier for you to take away the whole number and then the decimal. For example, first you do 30 - 3 which you know = 27. And now you take away the decimal so 27 - 0.60 = 26.4

Another method if you dont want to deal with the decimals is to multiply both numbers by 10 (depends on how many decimals) and then divide the answer by 10.

For example, 30 - 3.6 so you multiply both numbers by 10 so you have 300 - 36 = 264 so now you divide 264 by 10 which is 26.4 but this is MUCH troublesome than just doing a regular subtraction with decimals...

Last edited by LuisRodg (2008-03-24 04:10:48)

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: How to work this out not sure?

You set it up like a normal subtraction, but make sure that the decimal places are aligned. So:

  30
-  3.6
-------
  26.4

You can write 30.0 instead of 30 if it makes it clearer.

---

Why did the vector cross the road?
It wanted to be normal.

jmoore

Member

Registered: 2008-01-09

Posts: 25

Re: How to work this out not sure?

thanks i get it now