Urgent Maths help needed....

[adnanj]

(b) John has a length of string.
The string is 4 m long, correct to the nearest 10 cm.

(i) Write down the lower bound of the length of the string.
Give your answer in centimetres

(ii) John cuts off ten pieces of string.
Each piece is 5 cm long, correct to the nearest centimetre.
Find the minimum possible length of string remaining.
Give your answer in centimetres.

 

[SalmanPakRocks]

This is Limit of Accuracy right ?? Well first find the possible error and then subtract it to get the lower bound.
for (ii) The string remaining is of 3.5 m and you have to subtract the uperbound of the cut pieces of string from the actual string which is now 3.5 m.

 

[adnanj]

could u plz help in telling the answer and the way to obtain that???

 

[SalmanPakRocks]

well the thing is I m not sure if the answer is right but here is the P.E or possible error of first part. P.E = 5cm as 10/2 = 5cm.
so for part (i) Lower bound = 4m - 5cm therefore the answer is 3.95 m
and for part (ii) find possible error that is 0.5cm so the upperbound will be 5.5cm for one piece and for other pieces it would be 5.5*10 = 55cm so we will subtract it from 3.5m of string.
so the final answer = 3.5m - 0.55m = 2.95 m will be the final answer !!
hope i helped !!

 

[adnanj]

ur answer is absolutely right.. but how come the lower bound is 3.95?? according to me it should have been 3.5..

 

[adnanj]

i'll be really grateful if u help me how to determine the lower and upper bounds because this is sthg out of my mind...

 

[abcde]

AOA!
First, determine the possible error. In (b) (i), possible error = 10/2 = 5 cm. For lower bound, you subtract so the answer will be 400 cm - 5 cm = 395 cm or 3.95m.
For the second part, the possible error is different as the limit of accuracy is different. So P.E. = 1/2 = 0.5 cm. For upper bound, you add so the total max length of spring cut = (5 + 0.5) x 10 =55 cm. The lower bound of the string was 3.95 m so the answer will be = 3.95 - 0.55 = 3.40 m.
Is this clear?

 

[SalmanPakRocks]

ur answer is absolutely right.. but how come the lower bound is 3.95?? according to me it should have been 3.5..

ohh!!! well its just a tukka and i m very bad at this topic !!!

 

[adnanj]

AOA!
First, determine the possible error. In (b) (i), possible error = 10/2 = 5 cm. For lower bound, you subtract so the answer will be 400 cm - 5 cm = 395 cm or 3.95m.
For the second part, the possible error is different as the limit of accuracy is different. So P.E. = 1/2 = 0.5 cm. For upper bound, you add so the total max length of spring cut = (5 + 0.5) x 10 =55 cm. The lower bound of the string was 3.95 m so the answer will be = 3.95 - 0.55 = 3.40 m.
Is this clear?

walekumassalam.. could u plz tell how do we find the ossible error??because i haven't found this anywhere...if u could suggest any site where i could this topic or if u could explain.. please i really need to know this topic because i am not good at it at all...

 

[abcde]

The possible error is found by dividing the limit of accuracy by 2. So the possible error in (b) (i) is 10 cm/2 = 5 cm. And that in (b) (ii) is 1 cm/2 = 0.5 cm. Clear?

 

[adnanj]

thank u so much abcde

 

[abcde]

You're welcome! Throw your maths queries, I'll be happy to solve them...that is, if I can