37. David invested certain amount in three different schemes A, B and C with the rate of interest 10% p.a., 12% p.a. and 15% p.a. respectively. If the total interest accrued in one year was Rs. 3200 and the amount invested in Scheme C was 150% of the amount invested in Scheme A and 240% of the amount invested in Scheme B, what was the amount invested in Scheme B?

A. Rs 10000 B. Rs 8000 C. Rs 6500 D. Rs 5000

Answer Answer: Option D Explanation: Explanation:-Let x, y and z be the amounts invested in schemes A, B and C respectively. Then,
add individual interest to get total using Si= pxrxt/100
[x x 10 x 1]/100 + [y x 12 x 1]/100 + [z x 15 x 1]/100 = 3200
10x + 12y + 15z = 320000…. (i)Now, z = 240% of y =(12/5)y……… (ii)And, z = 150% of x =(3/2)x so,x=(2/3 )z = (2/3) x value of z from ii
x= (2/3) x (12/5) y = (8/5)y………..(iii)
From (i), (ii) and (iii), we have :
16y + 12y + 36y = 320000
64y = 320000
y = 5000
Sum invested in Scheme B = Rs. 5000

38. The SI on a sum of money will be Rs.2500 after 5 years. In the next 5 years Principal is trebled, what will be the total interest at the end of the 10th year?

A. Rs.15000 B. None of these C. Rs.10000 D. Rs.20000

Answer Answer: Option C Explanation: Trick: (n+1) * x i.e. (3+1) *2500
N= No. of times it become
X= SI