Institution: Bangladesh Development Bank Exam: Bangladesh Development Bank Ltd - Senior Officer - 24.11.2017
Topic: Arithmetic Mathematics (পাটিগণিত), Subject: Mathematics (সাধারণ গণিত)

Best Answer Explained in Below-:

To determine how many more games the cricket team must win to achieve a 70% overall win rate, we first find out their total target wins after all 90 games (60 already played plus 30 upcoming).

1. **Calculate Total Wins Needed for 70%**:
An overall win rate of 70% means the team needs to win 70% of 90 games:
\[
0.7 \times 90 = 63 \text{ wins required}
\]

2. **Current Wins**:
The team has already won 40 games.

3. **Wins Needed from Upcoming Games**:
To find out how many more games the team needs to win, we subtract their current wins from the total required wins:
\[
63 - 40 = 23 \text{ wins needed}
\]

4. **Confirming Total Games and Wins**:
If the team wins 23 out of the 30 remaining games, their total wins would be:
\[
40 + 23 = 63 \text{ wins}
\]
This matches the target for a 70% win rate.

Thus, they need to win 23 games to achieve a 70% win percentage. However, the answer option 'B' (25) might reflect a potential error in the problem or options as per understanding in a realistic scenario. Therefore, under strict mathematical interpretation, the clear number required to reach 70% based on the calculations is 23 wins out of 30 games, suggesting the solution may stem from misinterpretation originally proposed in the problem statement listing options inaccurately.