Gambhir shared 51 runs with Yusuf Pathan (27 off 17 balls) to take KKR total past 150 as RCB bowlers struck regularly after the home side chose to field at M Chinnaswamy Stadium.
Other KKR batsmen -- Jacques Kallis (16) and Manoj Tiwary (23) -- batted well but could not convert the starts into big knocks.
Gambhir survived a run-out after a mix-up with Kallis when he was on one. He cut the ball to the point and set off for a single but his partner was not interested in the run. Gambhir was lucky, a better throw from RCB captain Virat Kohli would have seen his back early on. He then cracked two magnificent boundaries off R P Singh.
Gambhir survived yet another run-out after the third umpire ruled that the wicketkeeper had not collected the ball cleanly before breaking the stumps. He then reached his 17th IPL fifty by gently nudging Jaydev Unadkat to third man.
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After crashing Unadkat for a six, Gambhir top-edged Vinay Kumar for the bowler to take a return catch.
Eoin Morgan followed suit as he was out on his fifth ball for two off R P Singh.