PUSH-UP WITH LEG LIFT

What it works: Chest, upper arms and core section
How to do it: Get into standard push-up position with your hands on a stable, raised platform and lift your right leg. Slowly bend your arms to lower your chest towards the platform and return to start position. Repeat 10 to 15 times with each leg raised.
CRUNCH

What it works: The abdominals
How to do it: Sit on the edge of a stable platform like a bench, with hands behind your head, and stretch your legs out. Using the abdominal muscles, lift your knees and upper body simultaneously and hold for a few seconds. Return to start position and repeat 10 to 15 times. If it's hard to balance on the platform, do it on the ground till your abs get stronger.
STEP-UP WITH DUMBBELL CURL

What it works: Legs, buttocks, upper arms and the core section
How to do it: Stand alongside a stable platform like a bench, put your left leg on it and hold a dumbbell in each hand. Using the muscles of the left leg, step up as you curl the dumbbells towards your shoulders. Return to start and repeat. Do 10 to 15 times with each leg. The balance required for this will work the core region too.