Help!

This is one way to think of it:

 

We know...

9 lags  =  20 lugs      Multiply both sides of this equation by  4 .

36 lags  =  80 lugs

 

And we know...

7 ligs  =  4 lags         Multiply both sides of this equation by  9 .

63 ligs  =  36 lags

 

63 ligs  =  36 lags       and       36 lags  =  80 lugs    So...

 

63 ligs  =  80 lugs

Excellent hectictar!

 

Here is another way:

1 lag = 7/4 ligs

7/4 ligs x 9 lags = 20 lugs

15.75 ligs = 20 lugs.       Multiply both sides by 4

63 ligs = 80 lugs.

On planet Larky, 7 ligs = 4 lags, and 9 lags = 20 lugs. How many ligs are equivalent to 80 lugs?

 

Here is a slightly different variation. Once you get the hang of this method you do not have to understand very much.

It all just falls out.

 

Think of them all as rates and write them as fractions.  Since they have units it is perfectly valid to turn the fractions upside down if that helps.   We have.

 

\(\frac{7\;ligs}{4\; lags}\qquad \frac{9\; lags}{20\;lugs}\qquad \frac{80\;lugs}{1}\qquad ?ligs\)

 

Ligs is what you want so put if first and on the top.      \(\frac{7\;ligs}{4\; lags}\)

 

Now you need to get rid of the lags on the bottom so find a fraction with lags and make sure lags is on the top, then put a mult sign between them.

 

\(\frac{7\;ligs}{4\; lags}\times \frac{9\; lags}{20\;lugs}\)

 

   Now the lags will cancel but you need to get rid of the lugs so multiply with lugs on the top.

 

\(\frac{7\;ligs}{4\; lags}\times \frac{9\; lags}{20\;lugs}\times \frac{80\;lugs}{1}\)

 

Now the lags cancel and the lugs cancel leaving you with just ligs on the top which is what you want.

 

\(\frac{7\;ligs}{4\; lags}\times \frac{9\; lags}{20\;lugs}\times \frac{80\;lugs}{1}\\ =\frac{7\;ligs}{4}\times \frac{9}{20}\times \frac{80}{1}\\ =7\times9 \;ligs\\ =63 \; ligs \)