To determine how many Lego planes Jonny can build in 40 minutes, we can set up a ratio based on the given information.
We know that Jonny can build 3 1/2 Lego planes in 60 minutes.
First, we need to convert the mixed fraction 3 1/2 to an improper fraction:
3 1/2 = (2*3 + 1)/2 = 7/2
So, Jonny can build 7/2 Lego planes in 60 minutes.
Now, let's set up a proportion to find out how many Lego planes Jonny can build in 40 minutes:
(7/2 planes) / (60 min) = x planes / 40 min
To solve for x, we can cross-multiply:
(7/2) * 40 = 60 * x
Simplifying the equation:
(7/2) * (2/1) * 20 = 60 * x
7 * 20 = 60 * x
140 = 60 * x
Dividing both sides of the equation by 60:
140 / 60 = x
2.33 = x
Therefore, Jonny can build approximately 2.33 Lego planes in 40 minutes. However, since we cannot build a fraction of a Lego plane, we can round down to the nearest whole number. Thus, Jonny can build 2 Lego planes in 40 minutes.