17.5%
.
Pradeep has 653 Rs. He sells mangoes for 23 Rs and guavas for 10 Rs.
The last digit of the 653 Rs can only be satisfied with the mangoes.
.
He sells either 1, 11, 21, 31 etc mangoes.
If he sells 1 or 11 mangoes, he needs to sell more guavas than mangoes ( [653 - 23 * 1 ] / 10 = 63 or [653 - 23 * 11 ] / 10 = 40).
If he sells 31 or more mangoes, he has at least 31 * 23 = 713 Rs.
.
Therefore he has sold 21 mangoes and ( [653 - 23 * 21 ] / 10 = ) 17 guavas.
He has bought the mangoes for 20 Rs (23 / 1.15) and the guavas for 8 Rs (10 / 1.25).
Thus he has spend 556 Rs (20 * 21 + 8 * 17).
His profit margin is thus 653 / 553 = 1.175 => 17.5%