first gym session

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hi , i am trying to work out the calories burned during my first gym session. I am 52yrs old, 236lbs, . Just a ball park figure would be good enough and i will buy a hrm as soon as possible. I did 15mins on treadmill at 4.5. Then 10mins on epileticle machine on quickstart.( nearly killed me) Then i did 4 differant weight machines doind 3 reps of 15 with 9kg weights on each. Then 15 mins on bike at 3.0. Can anyone help. I hope to build up my sessions, however am pleased with the first visit. I intend to go 3 times a week. I have already lost 35lbs with mfp and want to start with exercise. Any help appreciated.