Henry had 20 convertibles and 5 trucks in his miniature car collection. After Henry's aunt bought him some more miniature trucks, Henry noticed that a fifth of his collection were covertible. How many trucks did your aunt buy?

Henry had 20 convertibles and 5 trucks in his miniature car collection. After Henry's aunt bought him some more miniature trucks, Henry noticed that a fifth of his collection were convertible.

Now, to find the trucks her aunt buy.

Let the total collection of Henry be [tex]x.[/tex]

Number of trucks Henry had in his collection = 5.

Number of convertibles Henry had in his collection = 20.

As, Henry's [tex]\frac{1}{5}[/tex] collection were convertible.

Now, to get the total number of collection:

[tex]\frac{1}{5}\ of\ x=20.[/tex]

[tex]\frac{1}{5} \times x=20[/tex]

Multiplying both sides by 20 we get:

[tex]x=100.[/tex]

Total collection of Henry = 100.

So, the total number of trucks he had in his collection is:

Total collection of Henry - number of convertibles Henry had in his collection.

[tex]=100-20[/tex]

[tex]=80.[/tex]

Hence, Henry had total 80 trucks in his collection.

And 5 trucks he had already in his miniature car collection.

Now, to get the number of trucks her aunt buy we subtract trucks he had already in his miniature car collection from the total number of trucks in Henry's collection:

Total number of trucks in Henry's collection - Number of trucks already in his miniature car collection.

[tex]=80-5[/tex]

[tex]=75.[/tex]

Therefore, her aunt buy 75 trucks.