medium · SAT Math

An arborist recorded the height of a particular species of maple tree at various ages after planting. The table shows age (x, in years since planting) and height (y, in feet), the data used to construct a scatterplot: Age x (years) | Height y (ft) 1 | 6.0 2 | 7.9 3 | 9.8 4 | 11.5 5 | 13.4 6 | 15.0 7 | 17.1 8 | 18.6 Line of best fit: y = 1.8x + 4.2, where x = years since planting and y = predicted height of the tree in feet. Which statement correctly interprets the SLOPE of this line of best fit in context?

1. The model predicts the tree grows a total of 1.8 feet over every 4.2 years since it was planted, rather than 1.8 feet per year.
2. The model predicts that the tree's height decreases by about 1.8 feet for each additional year since it was planted.
3. The model predicts that, on average, the tree's height increases by about 1.8 feet for each additional year since it was planted.
4. The model predicts the tree was about 1.8 feet tall when it was planted, and its height then increases by about 4.2 feet every year after that.

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