Ketu Placement in the third house of chart
If the person has ketu in your third house in the horoscope, this person becomes active and valorous. Ketu here makes the native a courageous person. The physical constitution of such natives is likely to be strong and sturdy. It also gives a spiritual bent of mind. The person takes part in religious and virtuous activities and can also attain name and fame in these areas. Moreover, there is also a possibility of sudden money with this position.

When the planet of Ketu in afflicted in third house, it entangles your bond with siblings. It is not favorable for their health and longevity either. Younger siblings may face a lot of troubles in life. Ketu in 3rd house also makes your relationship with colleagues and associates inimical so care should be taken to keep your attitude with people in check. There is also a tendency to indulge in short travels frequently.

Generally speaking, Ketu shows favorable results when posited in third house. The person will be famous and wealthy and successful in life. This native will have a fear of god, religious and will have obedient children. Travelling will be fruitful with good earnings. All these results are possible only when Ketu is benefic here and has aspect of favorable planets or Ketu is placed in exalted state.
A Harmful Ketu will cause unnecessary travels resulting in waste of money and time. Relations with younger brother may not be cordial and the native may have to spend on legal complications with siblings or otherwise.

As a native with the planet of ketu in your third house of chart, If you have suffered from a malefic ketu, you can do the following; you can apply a tilak of saffron on the forehead, also you can offer jiggery in the flowing water and it will help you to wear gold, it will also help you to donate two colored blanket to poor people or in Bhairon Temple on Wednesday or Sunday. Alternatively he can also donate mustard oil on Saturday.