What is the name of this plant with mango type leaves?
This looks very much like a plant in the Ericaceae family, and specifically it looks to be some species of rhododendron. 


Shrubby looking tree/shrub
Spirally arranged stiff (appears evergreen) leaves 
Strong midrib on leaf
Large flower


 

With over 1000 species worldwide and more than 120 species known to occur in India, the picture likely doesn't have enough detail for someone without specific knowledge of Indian plant species to be able to ID to species. Even an expert might need the following details:


Exact leaf measurements, specific habitat details (elevation, distance to water, etc.) and closeups of leaf undersides, stem axils, bark and (opened) flower. A zoomed out picture showing the whole shrub/tree would also likely be helpful in IDing to species. 


I would recommend reading Mao (2010) The genus Rhododendron in north-east India. 


List of species and locations etc. 


 Disclaimer: I am not very familiar with Indian flora, so I could be unaware of genera/species that might be a better fit. Please try using a flora with dichotomous key to ID.