Hi PurvaG,shashag picked
p = 1 hour just to test the answers with a concrete number, so let's see where those three $20s come from.
The firm bills film in
15-minute blocks:
- The
first15 minutes cost
$140.
-
Every15-minute block after that costs
$20.
Now take
1 hour. One hour =
60 minutes, and
60 ÷
15 =
4 blocks of
15 minutes each. Line them up:
- Block
1 (
0-
15 min) -
$140 (this is the first-block price)
- Block
2 (
15-
30 min) -
$20- Block
3 (
30-
45 min) -
$20- Block
4 (
45-
60 min) -
$20So after the first block,
3 blocks are left, and each adds
$20. That's the
20 + 20 + 20. Total =
140 +
60 =
$200.
The key idea: the
$140 already pays for the first block, so you only charge
$20 for the
remaining blocks - here,
4 total minus
1 =
3 of them.
Quick check to lock it in: try
p = 0.5 hour (
30 minutes).
-
30 ÷
15 =
2 blocks.
- First block =
$140, then just
1 leftover block =
$20.
- Total =
$160.
Notice you always have (number of blocks -
1) of the
$20 charges. In algebra, the blocks are
{4p}, the leftovers are
{4p} -
1, and the cost is
140 +
20(
{4p} -
1) =
120 + 20{4p} - which is exactly choice
A.
Answer: APurvaG
how did you get the 20+20+20?