+226 A pair of boots weigh 0.8 kg. When they get wet they increase in weight by 0.7 %. How much do the boots weigh when wet?
a) 0.0056 kg
b) 0.056 kg
c) 0.0875 kg
d) 0.875 kg
Came across this on a randomly generated test, sadly haven't been able to find it again on the same test to double check it.
I thought this was well within my abilities but I couldn't get any of their answers.
The answer I come up with every time, through different methods is 0.8056 kg. Even without calculating this, this answer makes more sense than those supplied as it is only fractionally more than 0.8 kg, as 0.7 % increase should be. I've done;
0.8 * 1.007 = 0.8056
0.8 / 100 * 100.7 = 0.8056
0.8 / 100 * 0.7 = 0.0056 + 0.8 = 0.8056
I even cheated and used the % button on the calculator;
0.8 * 100.7 % and still got the same answer.
Can we just put this down to another typo' or have I missed something?
+118613 It is a typo (perhaps they meant to ask for the increase in weight)
You answer is perfect 
+226 Thanks again Melody.
I'm gaining more confidence to question them.
I've also had a bit of a go at the two factorising questions you set me, not easy!
+118613 Hi Tenacious,
I cannot remember what factorising questions I gave you - maybe they were too hard.
Maybe you could try these. If you don't know how to do them we can talk about it.
1) 3x+3
2) 6xy-9x
I am very happy to help you learn. We just need to work out a starting point
+118613 The 2 here are correct and the first one on the other thread is also correct.
When you cross reference threads it might be a good idea to do it in two directions - not just one :)
So I know know that you can pull out common factors to factorise but you do not know how to do quadratics.
quadratics fall into a number of different types so lets look at the easiest ones
first I am going to expand and then simplify this
$$\\(x+2)(x-3)\\
=x(x-3)+2(x-3)\\
=x^2-3x+2x-6\\
=x^2-x-6\\$$
Now I want to go the other direction and factorise.
$$\\x^2-x-6\\
=x^2-1x-6$$
Now I need 2 numbers that multiply to -6 and add to -1
Since they mult to give a negative number, one must be pos and one must be neg.
Since the add to a neg, the 'bigger' one must be the neg.
Must be -3 and +2 -3*2=-6 -3+2=-1 that works :)
the answer is
$$(x-3)(x+2)$$
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Your turn Tenacious
Factorise
$$\\1) x^2+7x+6\\
2) x^2+10x+21$$
+226 The question I couldn't get right in your previous challenge was x2+x+6, I still can't work this one out. Can you break this one down for me as it's slightly different to the one in your last post.
The next challenge.
1) x2+7x+6
= (x+1)(x+6)
= x2+6x+x+6
= x2+7x+6
2) x2+10x+21
= (x+3)(x+7)
= x2+7x+3x+21
= x2+10x+21
Without sounding too confident, these were fairly easy. You've still got me beat by your x2+x+6.
If I remember correctly, the questions you have given me are called trinomials, and by simplifying them into two brackets, I have factorised them. Are they then called quadratics once I have two sets of brackets with two terms in each? It makes sense in my head, 3 terms in trinomials and 4 terms in quadratics. Is this correct?
+118613 Mmm
I have always been a bit 'wishy' about these terms too.
https://www.mathsisfun.com/definitions/binomial.html
http://www.mathsisfun.com/algebra/quadratic-equation.html
They are using binomial here differently to how I would use it. 
These resources should help any way. Take a look.
-----------------------------------
Now, how do you factorise
$$\\x^2-x-6\\
=x^2-1x-6\\$$
Now you need 2 numbers that mult to -6 and add to -1 What will they bee be?
------------------------------------
$$x^2+x+6$$
cannot be done this way because there are no 'obvious' numbers that multiply to 6 and add to 1
I do not think that i actually gave you this question :)
In fact there are no real solutions to this one at all! Only imaginary solutions and you do not need to worry about those yet, LOL
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+118613 You know, as a member and the poster of a question you can give points. :)
+226 Ah yes, so the trinomial was right but the quadratic comes from the term being squared not the four terms in two brackets as I thought. So I would say the question you have set below is a quadratic trinomial.
Let's try this one;
x2-x-6 Not too difficult
= (x-3)(x+2)
= x2+2x-3x-6
= x2-x-6
x2+x+6 Yes, this definitely came from you from Jan 18th. I guess it was just a typo. Don't worry though, it did it's job, definitely got my brain working to try every possible answer for it. Glad it turns out that it can't be done though, thought I was just incapable.
I have been awarding points here and there to say thanks, probably not all posts though, I've not really kept count.
