Henry had 20 convertibles and 5 trucks in his miniature car collection. after henry's aunt bought him some more miniature trucks, henry found that one-fifth of his collection consisted of convertibles .how many trucks did his aunt buy?

75

Step-by-step explanation:

Henry started with 20 convertibles and 5 trucks.

His aunt bought him x miniature trucks.

Now, his convertibles represent 1/5 of his collection.  How many trucks did her aunt buy?

So, if his convertible represent 1/5 of his collection now, that means his collection is 5 times larger than the number of convertibles.  We know he has 20 convertibles... so the collection now counts 100 (5 * 20) items.

Out of 100 items, we remove the 20 convertibles to get a total of 80 trucks.

Then we subtract the initial 5 trucks... so, his aunt bought him 75 trucks.

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.