Search 80,994 tutors

This is a mole ratio problem - with the added twist of using the ideal gas law to convert the answer in moles to an answer in liters.   Convert the grams of Li to moles:   (34.2g)/(6.941 g/mol) = 4.927 moles of Li   Looking at the balanced eqn: 2 moles...

If you want 12 L total, then you can say use v L of the 20% solution.  Then you need the rest of it, or 12-v L, to be the 50% solution.   You want to end up with 12L OF a 30% solution.  Say this is salt solution.  You would have 30 parts salt for every 100 parts of solution...

The shortcut is to remember that when you are multiplying by 10, 100, 1000, or 10000,... you move the decimal place in the number you are multiplying TO THE RIGHT (i.e., make the number BIGGER) by the number of zeros you see in the 10, 100, 1000, 10000,...   That is readily seen:  4...

The trick here is making all your units work out.  Remember that units cancel like fractions reduce.   Let's break it down.   In one day you have 2 10W bulbs lit for 1 hr.  That makes: 2 x 10W X 1 hr = 20 Watt-hours   Notice they give you a cost...

If Sarah takes 5 hours to mow the lawn, then Sarah's rate of mowing the lawn is 1 lawn/5 hours.  This is equal to (1/5) lawn per hour, or 0.2 lawn/hr.   If Karen mows the lawn 5 times faster, then she takes LESS time to mow the lawn than Sarah.  Karen takes 5 times less time...

SAS means the 2 triangles has two sides and the angle between those 2 sides congruent. You have to be able to trace your pencil through the side, angle, side without lifting it, and prove that in the other triangle, you can make the same tracing.  Order is important.     You...

1.  (4+2i) - (6-8i):   distribute the minus sign:   = 4 + 2i - 6 + 8i   gather like terms:   = -2 + 10i   2. i18 = i times 18.  You should write it as 0 + 18i to give the answer in the form asked for.   3...

Sequence 1 = (n+2)/[(n+3)^2] Sequence 2 = 1/[2^n]   These problems can be difficult. It takes looking for patterns, and that comes more easily with practice. Remember the first term, n=1, second n=2,...

Many students like cross multiplication for problems like this.  Write the fractions vertically, each with a top and a bottom.  Draw a big X through the problem.  This X will connect the 25 to the 12 and the 60 to the s.   The equation is then rewritten as   (25)(12)...

Let's "read and write" exactly what the question says:    The sum of the interior angles of a regular polygon IS:   sum interior =       180 degrees less than... (something):   sum interior = (something) - 180       three...

Percent literally means per 100.  Whenever you see the word percent, or the symbol %, take whatever is before it, and put it over 100.   So 125% = 125/100.  That can be reduced to 5/4.     To convert to a decimal, you can do long division, dividing 5 into...

Isotopes.   Remember - iso - as a prefix, means it has something the same. Isoceles triangle - 2 of the same sides/angles.   Isomer - 2 chemicals that have the same formula/weight.  You'll learn other iso- words in science.   Short simple videos in science are...

I get 22.5.  But you can check the math.  Here's how you solve the problem:     If the scoops are squished, there are no air spaces.   Therefore you can set:   Vscoop .  (# scoops) = Vcone    So (# scoops) = [Vcone...

To answer these questions without the aid of a calculator, you have understand some basic definitions and rules.  To get a LOG (and this is the LOG in base 10, because when the base is unstated, we set it to 10), the question you have answer is:  what power do I need to raise 10 to, to...

To begin graphing an inequality, you start just like graphing an equation with an = sign.  Your second equation is the easier, so let's start with that. y< or = -4.  Find y=4, draw across as a solid line (horizontal line to indicate all values of x are valid), and then...

Hi Kaela.  A proportion is simply a comparison of 2 fractions.  Like "part over whole" = "part over whole".  Whenever you are doing proportions, just make sure you "keep the top with the top and the "bottom with the bottom".  That's a nonsensical...

Hi Elizabeth.  Ralph already gave you a nice simple answer.  But one way to remember this for good is by thinking through a simple example.  If I asked you to solve 2(3+5), I am sure you would tell me - that easy!  Just add the 3 and 5, so that becomes 2(8) = 16.  But...

Hi Heather.  I usually tell my students to solve these word problems by writing down EXACTLY what it says - "in math".  Your problems starts "3 of 4 numbers have a sum of 22".  So we'll write a+b+c = 22.  (I simply chose to call the 4 #s a, b,...

Hi Sonya.  Richard S. already gave you a nice explanation of how to do this problem.  Here are some general things to keep in mind.  When doing an algebra problem where you have to solve for a variable (in your case, z) - remember your goal is to get z alone.  It'll usually...

(NOTE: You should see exponents (superscripts (and not ^)) throughout this explanation. If you are not seeing superscripts, the answer is not displaying correctly.) Hi Mathalina.   PEMDAS says you should really start with P: inside the parenthesis first, but there's not much...