The phrase “delivered on” is idiomatically correct for fulfilling or meeting an expectation, particularly in reference to promises or plans. “He never delivered on the grandiose promises” means he failed to fulfill the ambitious promises he made.
Arun’s present age in years is 40% of Barun’s. In another few years, Arun’s age will be half of Barun’s. By what percentage will Barun’s age increase during this period?