It is the rainy season in central Texas.  It rained for 7 hours on Monday at a rate of 1 inch per hour.  On Tuesday, it rained for 4 hours at a rate of 2 inches per hour, and on Wednesday, it rained for 2 hours at a rate of twice that of the previous day.  What is the total combined rainfall, in inches, for these three days?
On Monday, 7 hours of rain at a rate of 1 inch per hour is 7*1=
<gadget id="calculator">7*1</gadget>
<output>7</output>
7 inches of rain.
On Tuesday, 4 hours of rain at a rate of 2 inches per hour is 4*2=
<gadget id="calculator">4*2</gadget>
<output>8</output>
8 inches of rain.
Twice the rate of Tuesday is 2*2=
<gadget id="calculator">2*2</gadget>
<output>4</output>
4 inches per hour.
Wednesday, 2 hours of rain at a rate of 4 inches per hour is 2*4=
<gadget id="calculator">2*4</gadget>
<output>8</output>
8 inches of rain.
The combined total of the rainfall for these three days is 7+8+8=
<gadget id="calculator">7+8+8</gadget>
<output>23</output>
23 inches of rain.

<result>23</result>