Question 175289
Ok, on this type of problem, you need to use the concept of weighted averages.
Let's say that there are x words in the article being type-written. 
Now Jose, typing at 60 wpm, would take {{{(x/2)/60 = x/120}}} minutes to type half the article while Vishna, typing at 40 wpm would take {{{(x/2)/40 = x/80}}} minutes to type half the article. Adding these two rates, we get:
{{{(x/120)+(x/80) = 5x/240}}} which reduces to:
{{{x/48}}} so the combined typing speed to type the article is 48 words per minutes.