Math Group at eNotes

This is a problem on ratio and proportion. We can do the problem in ...

Mon, 14 Dec 2009 19:21:15 PST

This is a problem on ratio and proportion. We can do the problem in the usual ratio and proportion way itself. It is asked to find the fourth proportion. Here the product of first and fourth term are equal to the product of middle terms. So, first term*fourth term = 10*x . The product of middle terms = 1*20. Therefore, 10x = 20 and solve for x. So, x = 20/10 = 2.

While the above answer is, of course, correct, I'd like to explain how...

Mon, 14 Dec 2009 16:31:28 PST

While the above answer is, of course, correct, I'd like to explain how to get the answer in hopes that an explanation might help you do other problems like this on your own. What you're being asked here is essentially this equation: 10/1=20/x The most usual way to find for x when you have an equation like this is to cross-multiply. That is, you multiply the top of one fraction by the bottom of the other. That gets you 10X=20 You then divide...

Lol, apparently you are not in 10th grade. I did this in 7th. Easy work...

Mon, 14 Dec 2009 16:11:45 PST

Lol, apparently you are not in 10th grade. I did this in 7th. Easy work so here we go :) You have to isolate the variable X , so you need to divide -5 by 3. that would be -1.66 repeating, rounding to -2. So X= -1.66 OR X= -2 if you ROUND. Hope this helps. :)

10:1=20:2 x=2

Mon, 14 Dec 2009 16:08:27 PST

10:1=20:2 x=2

find x 10:1=20:x

Mon, 14 Dec 2009 15:59:54 PST

find x 10:1=20:x

It is not possible to determine the perimeter of a triangle given what...

Mon, 14 Dec 2009 10:53:10 PST

It is not possible to determine the perimeter of a triangle given what you have provided here. It is certainly possible to find the area of a triangle given the base and the height. The formula for that is area = 1/2base*height. So the area of your triangle is 36 square inches. But if all we have is the base and the height, we can't find the perimeter. If we knew, for example, that this was a right triangle, then we could find the...

Problem Solving

What is the perimeter? The base and height of a triangle with base 12...

Mon, 14 Dec 2009 10:07:49 PST

What is the perimeter? The base and height of a triangle with base 12 in. and height 6 in.

Here the speed of the Mahila and Ahin are to be determined. Let it be...

Mon, 14 Dec 2009 09:41:52 PST

Here the speed of the Mahila and Ahin are to be determined. Let it be x km/h for Mahila.Then , Ashin's speed is x+5 km/h The time taken by Mahila for 50 kms =50/x ...........(1) The time taken by Ashin tofor 40 kms = 40(x+5)....(2) By the condition that Mahila takes 2 hours extra for her 50kms than that of Ashin for 40kms, we get the relation between (1) and (2): 50/x hrs- 40/(x+5) hrs = 2 hrs.......(3). Now solve for x and you get Mahilas...

We know that distance = speed*time. So we can set up equations. Let...

Mon, 14 Dec 2009 08:57:30 PST

We know that distance = speed*time. So we can set up equations. Let Ashin's speed be x. That means that Maliha's speed is x-5. So now we know that 40/x = 50/(x-5) - 2 because the time it took Maliha to go 50 km at her speed is 2 hours more than it took Ashin to go 40 km at her speed. So then what you need to do is multiply both sides by x(x-5) That will get you 40 (x-5) = 50x -2x(x-5) Eventually, this will simplify down to 0 = x^2-10x-100...

How to find these function composition

Mon, 14 Dec 2009 07:33:36 PST

We have 3 functions, f,g,h:R->R, where f(x)=|x|, g(x)=6x-8, h(x)=4-x

u=?, where u=f*[(g*f)/h], "*" means composition of function

It takes Maliha two hours more to complete a 50 km journey than it takes...

Mon, 14 Dec 2009 07:27:56 PST

It takes Maliha two hours more to complete a 50 km journey than it takes ashin to complete a 40 km journey. If the average speed of Maliha for the...

What numbers should the supplier specify so that the probability of...

Mon, 14 Dec 2009 01:20:47 PST

What numbers should the supplier specify so that the probability of rejection of a door is at most 5%? Under given circumstances.

jayjay, when converting from Celsiusto Fahrenheit, the best way to do it...

Mon, 14 Dec 2009 00:26:15 PST

jayjay, when converting from Celsiusto Fahrenheit, the best way to do it is to realize that they have similar log scales and can be determined by knowing only one step, actually. To go from F to C to go from C to F 1) add 40 1) add 40 2) multiply by 5/9 2) multiply by 9/5 3) subtract...

Clearly, the first two answers give you the correct answer for how long...

Sun, 13 Dec 2009 20:44:34 PST

Clearly, the first two answers give you the correct answer for how long it takes to reach 40 grams of your element. But I think it might be helpful to explain a little bit about why you should set your equations up the way they did. If you think about it, what you are doing here is just like figuring the interest on an investment (only you are getting negative interest since your "investment" is decaying, not growing). When you try to...

When the material is decaying at the rate of p percent per hour the...

Sun, 13 Dec 2009 19:53:08 PST

When the material is decaying at the rate of p percent per hour the percentage of material left after n (Qn) hours is given by the formula: Qn = 100*[(100-p)/100]^n Given: p = 12 and Original quantity = 100 g Final quantity = 40 grams Therefore final quantity expressed as percentage of initial quantity = Qn = (40/100)*100 = 40 Substituting values of Qn and p in the above equation for Qn we get: 40 = 100*[(100 - 12)/100]^n = 100*0.88^n...

Since the element is decaying 12% per hour, the remaining of it is...

Sun, 13 Dec 2009 19:44:18 PST

Since the element is decaying 12% per hour, the remaining of it is =(100-12)% = 88% =0.88 of the original mass. Therefore the mass remaining after x hours = (0.88)^x = 40% =0.4 of the original mass. So, by taking logarithms on both sides, we get: x*log(0.88) = log (0.4) or x = log(0.4)/log(0.88) or =7.167852346 hrs = 7hrs 10 minutes 4.2684456 secs

y = 2^x is an exponential function. Let us substitute, x = 2u, then...

Sun, 13 Dec 2009 19:36:02 PST

y = 2^x is an exponential function. Let us substitute, x = 2u, then the function changes to : y=2^2u. But in graph, y=2^2x and y = 2^2u are the same except the fact that axis and x coordinates are called u axis and u coordinates respectively. Also, u=x/2. Implies, y values in y=2^2x is equal to y value of double the x coodinte of y=2^x. Since this is an exponential function of base 2, y=2^x. And y = 2^2x = (2^x)^2= square of the y...

Describe the geometrical transformation which would change the graph of...

Sun, 13 Dec 2009 19:16:05 PST

Describe the geometrical transformation which would change the graph of y=2^x to the graph of y=2^2x.

An element is decaying at a rate of 12% per hour. Initially we have...

Sun, 13 Dec 2009 19:00:27 PST

An element is decaying at a rate of 12% per hour. Initially we have 100g. When will there be 40g left?