Problem Solving

I always seem to have problems with conversions, can someone explain this question?
Thanks!



Correct answer is C



This looked pretty straightforward....till I got it wrong. Help me with my error.

Thanks!

X m/s = Y km/hr

km/hr can be rewritten as 1000m/3600s

X m/s = Y1000m/3600s

m and s cancel out, so Isolating Y...

Y= 3600X/1000 = 18X/5 (C)

As for the 2nd problem...

ABCD all have possible choices that make the solution a straight line.

eg. x^4 >=1 x=2,3,....or -2,-3....

Choice E states that the line 3x+4 is constrained at two ends

3x+4 >=2 so x>=-2/3
3x+4 <=6 so x<=2/3

so the line 3x+4 is constrained at -2/3<=X<=2/3

so E is the answer

Thanks jrbrown2.

For the second question, it said finite line, so I eliminated options A, B & C, but couldn't decide between D or E.

How is D not finite? It looks like its constricted by 2 & 5.

Thanks

For question 1,
Did you mean m & s cancels out after you isolate Y?

Also, I always get confused when I have to setup equations like this.....when the question says 'what is A in terms of B', how do I set that up as an equation?
For questions like "what is a% of b", I typically write 'x=a/100* b', but with 'in terms of' questions, I don't quite know how to write that.

Can you help?

Thanks!

D says that x is between 2 and 5 inclusive, so x can be 2,3,4, or 5

To rewrite:
x=2
x=3
x=4
x=5

they are all straight lines without constraints

when the question says 'what is A in terms of B', how do I set that up as an equation?

When a question asks this there are usually two equations (with different variables) that are equal to each other.

In this case x m/s and y km/hr. Equate the two equations, making sure to keep the units constant (i.e. km=1000m, 1 hr = 3600s).

x m/s = y km/hr
x m/s = y (1000m)/(3600s)

Isolating y,

y = x m*3600s/(1000m*s) <----the m and s cancel out here
and simplify

y=18x/5

Thanks for the explanation!

I think I understood the second Q as being plotted on the NUMBER LINE... not the coordinate system...

In that case how to decide between D & E?

Yes, its on the number line and that was where I got stuck as well. If I followed through with the calculations, I would've realized E was the answer.


For E- if you subtract -4 from all 3 parts of the equation like so:
2<=3x+4<=6
-4 -4 -4

You get: -2<=3x<=2
which when broken into 2 parts:
-2<3x>= -2/3
And 3x<=2 which gives you x<2>=-2/3 and x<= 2/3.

Hope that helps.