A building has 20 floors. Each floor is 3 meters high, except for the last two floors. The last two floors are each 0.5 meters higher. How tall is the building?
There are 20 - 2 = 
<gadget id="calculator">20-2</gadget>
<output>18</output>
18 floors that are each 3 meters high.
So the first 18 floors is 18 x 3 = 
<gadget id="calculator">18*3</gadget>
<output>54</output>
54 meters high.
The last two floors are each 3 + 0.5 = 
<gadget id="calculator">3+0.5</gadget>
<output>3.5</output>
3.5 meters high.
So the total height of the last two floors is 3.5 x 2 = 
<gadget id="calculator">3.5*2</gadget>
<output>7</output>
7 meters.
Therefore, the building is 54 + 7 = 
<gadget id="calculator">54+7</gadget>
<output>61</output>
61 meters high.

<result>61</result>