Important for :

1

D

S.I. = | P × r × t |

100 |

9000 = | 9000 × r × 4 |

100 |

r = 25%

New rate = 25 + 5 = 30%

9000 = 9000 × 30% × t

t = 3 | 1 | years |

3 |

Hence, option D is correct.

2

B

Amount = simple interest + principal⇒ 9200 = simple interest + 8000

⇒ simple interest = 9200 – 8000

= Rs 1200

if r % be the rate of interest ,

Then from, simple interest = | principal × rate% × time |

100 |

1200 = | 8000 × r × 3 |

100 |

⇒ r = 5%

2% more interest that is 7% interest

simple interest = | 8000 × 7 × 3 |

100 |

= Rs 1680

thus amount he will get is Rs 8000 + Rs 1680 = Rs 9680

Hence, option B is correct.

3

D

Let Rajat lend the sum at x% rate to the second friend.

According to the question,

15% × 10000 + x% of 10000 = 20% of 20000

⇒ 15 × 100 + 100x = 20 × 200

⇒ 100x = 4000 – 1500

⇒ 100x = 2500 ⇒ x = 25

Hence, the required rate of interest is 25% p.a.

Therefore, Option D is correct.

Therefore, Option D is correct.

4

B

Let the sum be P.Then, | P × 7 × 23 | – | P × 7 × 19 | = 672 |

12 × 100 | 12 × 100 |

or, 161P – 133P = 672 × 100 × 12

∴ P = |
672 × 100 × 12 | = Rs. 28800 |

28 |

Hence, option (B) is correct.

5

C

Given that:Simple interest for 10 years = Rs, 500

Therefore, SI for 1 year = Rs, 50

Therefore, SI for 5 years = Rs. 250

Now, if the principal is made four times, the interest will also become four times.

Therefore, SI for next 5 years = Rs, 250 x 4 = Rs, 1000

Hence, total interest after 10 years = 250 + 1000 = Rs, 1250

Therefore, option (C) is correct.