1 , 3 , 6 , 10 , 15 1) What is the nth term of the sequence?

2) Use the nth term to work out the 21st term of the sequence.

First difference,

Second difference,

Third difference,

And so on.

Assuming the pattern holds on, we see that

i-th difference,

Then, nth term is,

Now, the 21st term in the sequence is,

d. millimeters per hour.

step-by-step explanation:

we are given that,

carlo used a rain gauge to measure the amount of water his lawn is receiving from the sprinklers.

since, according to the options, we see that,

water cannot be measured by 'miles per hour', 'meters per second' and 'grams per seconds'.

we get that, the water can be measured by 'millimeters per hour'.

hence, the appropriate rate for describing the amount of water is 'millimeters per hour'.