Adithi S.

asked • 06/08/16

the cost of 3 1/2 kg of sugar is rs.63. find the cost of 1 3/4 kg of sugar

with the answer and the steps

1 Expert Answer

By:

Mark O. answered • 06/08/16

Tutor
5.0 (167)

Learn Physics, Math, and Comp Sci from Professional Scientist

See tutors like this
See tutors like this
Hi Adithi,
 
3 1/2 kg of sugar costs 63 rupees
 
3 1/2 kg = 7/2 kg
 
We want to find out how much 1 3/4 kg of sugar costs. Let's call this amount x.
1 3/4 kg = 7/4 kg
 
We can form an equation of proportions:
 
(7/4 kg) / (7/2 kg) = (x rupees)/(63 rupees)
 
(7/4) / (7/2) = (7/4)*(2/7) = 1/2
 
So, 1/2 = x/63
 
This yields
 
x = 63/2 = 31.5 rupees through cross multiplication
 
So, 1 3/4 kg of sugar costs 31.5 rupees.
 
 
Upvote • 1 Downvote
More
Report

Adithi S.

sir no it is Rs-63 and sir can you give the answer for my question with steps right now as it is very urgent pls sir mark
 
Report

06/08/16

Mark O.

Is this 63 rupees?
Report

06/08/16

Adithi S.

yes sir
 
Report

06/08/16

Mark O.

Is that answer clear?
Report

06/08/16

Adithi S.

sir, i cant understand because i got the answer as 22 1/2 and in my textbook the answer is  31 1/2  how is it possible as it the topic of rational numbers and sir you ot 31.5 rupees
 
Report

06/08/16

Mark O.

Hi Aditha. 31.5 is the same as 31 1/2.
 
I saw that you were focusing on rational numbers, this is why I tried to keep the expressions as fractions through the problem. But, 31.5 is the same as 31 1/2.
Report

06/08/16

Mark O.

Are you okay with this answer?
Report

06/08/16

Adithi S.

sir can you do the steps more clearly one by one as in my process of rational numbers i am grade 8 sir like this,
 
cost of 31/2 kg of sugar=''
cot of 13/4 kg''''''''=6*3 1/2
=63/1*7/2=441/2
=22 1/2
 
so sir can you do the same way without changing my steps but the answer should be 31 1/2 sir pls and say me where did i go wrong
Report

06/08/16

Adithi S.

statement wise as it is the same way in my textbook named ActiveTeach Universal Mathematics class 8 sir
Report

06/08/16

Mark O.

cost of 3 1/2 kg =  7/2 kg of sugar = 63
cost of 1 3/4 kg  = 7/4 kg of sugar= x
 
Form a proportionality equation:
 
(7/4 kg of sugar) / (7/2 kg of sugar) = x/63
 
Cross multiply the 63 to solve for x.
 
(63)(7/4) / (7/2) = x
 
(441/4) / (7/2) = x
 
(441/4)*(2/7) = x
 
882/28 = x
 
441/14 = x
 
So, x =31 1/2
 
How is that? 
Report

06/08/16

Adithi S.

yes sir but is this rational number method only
 
 
Report

06/08/16

Adithi S.

sir but in our textbook there was no x method and ratio and proportion method sir i want original correct rational method only sir please 
Report

06/08/16

Mark O.

Hi Aditha,
 
Yes, rational means fraction. In that last answer, I was careful to only write fractions, or rational numbers.
Report

06/08/16

Mark O.

Are you all good now?
Report

06/08/16

Mark O.

1.       -15abc - 35a3
      - (-25abc + 16a3)
       --------------------
 
 
or
 
         -15abc - 35a3
         +25abc - 16a3)
       --------------------
       10abc - 51a3
 
 
2. (23x2 - 11xy + 15y2) + something = -3x2 + 22xy -5y2
 
To solve for the something, subtract the first expression from each side of the equation:
 
 (23x2 - 11xy + 15y2) - (23x2 - 11xy + 15y2) + something = (-3x2 + 22xy -5y2) - (23x2 - 11xy + 15y2)
 
which leads to
 
something = -3x2 - 23x2 + 22xy + 11xy - 5y2 - 15 y2
 
So,
 
something = -26x2 + 33xy -20y2
 
3a.
1/2abc * -4ab2
 
(1/2)(4)a*ab*b2*c  Multiple like things together: number times number, powers of a, powers of b, etc.
 = 2a2b3c
 
3b.
 
 -5x2y2 * 5y2x2
 
= -(5)(5)x2x2y2y2
 
 = 25x2+2y2+2
 
= 25x4y4
Report

06/08/16

Mark O.

This is a forum where tutors work problems for free in hopes of attracting new students. All of the tutors on here charge a fee for services, and they are all working for free. Don't worry about paying anything.
Report

06/08/16

Mark O.

Yes, for 3a I forgot the negative sign from the -4. Indeed the answer is -2a2b3c. 
 
For 1, as written I am right and your book is wrong. for your book to be right, there should be no negative sign in front of 25abc. You may want to double-check to see if you copied the problem correctly.
Report

06/08/16

Mark O.

My number 2 is right. It does not matter what order you add the terms
 
I forgot the negative sign in my multiplication for 3b as well. Sorry about that. Your answer is correct.
Report

06/08/16

Adithi S.

hi sir
Report

06/08/16

Still looking for help? Get the right answer, fast.

Ask a question for free

Get a free answer to a quick problem.
Most questions answered within 4 hours.

OR

Find an Online Tutor Now

Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.