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? Think carefully first, then make a decision:
There are 20 - 2 = 18 floors that are each 3 meters high. So the first 18 floors is 18 x 3 = 54 meters high. The last two floors are each 3 + 0.5 = 3.5 meters high. So the total height of the last two floors is 3.5 x 2 = 7 meters. Therefore, the building is 54 + 7 = 61 meters high. So, the answer is 61.