Don't be stupid man. Overall fitness is the key, not just pushups. If you do 120 pushups and 120 situps, then fail the run, it won't matter how many pushups you did. You still failed the PRT.
I was a PRT Coordinator before I went to OCS. I was also stashed at NRD giving pro-recc'ed candidates PRTs for their final select paperwork. I saw too many people go all out on the pushups and situps, then drag ass on the run.
Look at your age group and find the maximums. Do it perfectly, till you hit the max, then take a knee and move on to the next. Your objective is to hit your maximum pushups and situps, after you run a quarter mile, do dynamic stretching (jog in place, etc etc), bearcrawl to the track, do another quarter mile of jogging forward/sideways/backwards and lunges *then* you start the pushups and situps.
And of course, the run is right afterwards too, which makes or breaks people's overall performance. So you want to have some energy left over for the run. You're gonna get the same pushups score as a 22 year old whether you do 107 pushups or 87 pushups, keep some gas in the tank. There's gonna be a time when you'll need it. For me, I really needed it for my out PFA. I was hacking and sick like a dog that day, infecting everyone else in my class. I did max pushups/situps, then 9:20 on the run, got 295 out of 300 for my age group plus an individual achievement for Physical Fitness.
Also, I might want to add that when you get beat, pushups are the least of your worries. Anyone can do pushups. It's the other exercises that induces pain, no matter what shape you're in - it's gonna hurt. Bearcrawling, starjumpers, 8-counts, burpees, monkey fuckers. Jog in place holding your M1 rifle right in front of you, straight arms (that sucks!).