1st AP : 3,6,9,12,....... upto 78 terms t78=3+(78−1)3 =3+77×3 =234 2nd AP: 5,9,13,17,...... upto 59 terms t59=5+(59−1)4 =5+58×4 =237 Common term's AP : First term =9 Common difference of first AP=3 And common difference of second AP=4 ∴ Common difference of common terms AP=LCM(3,4)=12 ∴ New AP =9,21,33,...... tn=9+(n−1)12≤234 ⇒n≤