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### Answers :-

1. (a) Principal = Rs. 2550,

Rate¿ = 4¿ = 26/25 (26 → Installment, 25 →

Principal)

Time = 25× 26 : 26× 26

IInd year 625 : 676

Note: Installment will be same in both cases.

According to the question,

1275 units = Rs. 2550

1 unit = Rs. 2550/1275

676 units = Rs. 2550/1275 × 676

Rs. 1352

2.(d)

3. (d) 540 = P × R × 3/100

PR = = 18000 …………… (i)

CI = P [(1 + R/100)2 – 1]

376.20 = P [(1 + R/100)2 – 1]

= P [R2/(100)2 + 2PR/100]

= 18000 × R/(100)2 + 2× (18000/100)

= 376.20 = 18 × R/10 + 360

= 376.20 – 360 = 18R/10

R = 162/18 = 9%

From (i) P × R = 18000

P × 9 = 18000

P = Rs. 2000

4. (a) Rate 8 % = 35/4% = 7/80 = 2/25

5. (d) Amount after three years = Rs. 2662

Amount after two years = Rs. 2420

→ Net interest earned in the 3rd. = 2662 – 2420 =

Rs. 242

→ Rate of interest (r) = 242/2420× 100 = 10¿

Thus 2nd year’s amount is principal for 3rd year

6. (d) Given Amt. = Rs. 12100

R% = 10% = 1/10

Time = 2 years

Total amount for 2 year

= 10 + 10 + 1 + 10 = 121

→ 121 units → Rs. 12100

→ 1 unit → 100

→ Principal = 100 unit

= 100 × 100 = 10000

7. (d) Compound Interest = Rs. 1361,

Time = 3 years, Rate % = 5 % = 1/20

According to the question,

1261 units = Rs. 11261

1 unit = Rs. 1261/1261 = Rs. 1

8000 units = 8000 × 1 = Rs. 8000

Thus, Hence Required Principal = Rs. 8000

8. (c) Rate% = 4% time = (t1)= 1 year

Amount = Rs. 7803

When interest is compounded half-yearly

New Rate% = 4/2 = 2%

Time = 1 × 2 = 2 years

Required Rate% for 2 years CI

= 2 + 2 + (2 × 2)/100 = 4.04%

According to the question,

(100 + 4.04)% of sum = Rs. 7803

Sum = 7803/104.04 × 100 = Rs. 7500

Alternate:

Time = 2 years,

Rate% = 4/2, 2% = 1/50

According to the question,

2601 units = Rs. 7803/2601 = Rs. 3

2500 units = Rs. 3 × 2500 = 7500 Rs.

Thus, Hence Sum = Rs. 7500

9. (b)

Since Installment is equal hence multiply equation (i)

by 21

→ total principal = 420 + 400 = 820 units

→ 820 units → Rs. 15

→ 441 units → Rs. 6615

→ Each installment

= Rs. 6615

10. (b) Principal = Rs. 21000

Rate = 10¿ = 1/10 = 11/10 (11 → Installment, 10

→ Principal)