I agree with Jura when she says 'one hundred laughs equal ten minutes' running', but I would also point out there are similar situations where the singular verb would be correct: One hundred dollars is a lot to pay for a two course dinner! One hundred days is too long to have to wait for a parcel delivery! You have a plural subject, yet you also have a singular verb! I guess the explanation for this phenomenon is that in the first example we mean the sum of one hundred dollars ... and in the second example we mean the period of one hundred days .... Back to your example. I can't see any obvious, singular noun that could or would be associated with the phrase 100 laughs, therefore I think a plural verb is called for. You could also re-cast the sentence: As far as calories are concerned, laughing one hundred times is equivalent to running for ten minutes.

It's standard in English to use "equals" to give a result when talking about mathematics. The thinking behind this is, "the sum of X (plus Y) equals Z". So "the sum" or "the total" is a hidden and singular subject.

Correction: One hundred LAUGHS EQUAL ten mintues of running or ONE LAUGH EQUALS ten mintues of running.