O-Level Additional Math

[lost boy]

Urgent! Please answer as quickly as possible. I have no idea whether this is related to mathematics because its an arithmetic progressions question. This is a Secondary one question


Q1. Find the sum of the first N odd numbers.
Q2. Find the sum of the first n natural numbers
Q3. Write down three integers in A.P whose produce is a prime number

[pinkapple]

lost boy:

Urgent! Please answer as quickly as possible. I have no idea whether this is related to mathematics because its an arithmetic progressions question. This is a Secondary one question


Q1. Find the sum of the first N odd numbers.
Q2. Find the sum of the first n odd numbers
Q3. Write down three integers in A.P whose produce is a prime number

eh.. 1st 2 questions same mah

[lost boy]

I had changed q 2 . Ps show me the working . Thanks.

[pinkapple]

answer to Q2: http://www.9math.com/book/sum-first-n-natural-numbers

look at the picture. it'll help.

from here, try to answer Q1 yourself.

As for Q3, think what is the definition of prime numbers.
then what are integers.
work from here. tell u the answer tmrw.

[S-H]

Hi can someone help me with this question, thank you!


The curve y=ax^3+bx^2+c passes throught the points (-1,0) and (0,5). If the tangent to the curve at the point x=1 is parallel to the x-axis, find the values of a, b and c.

[jieheng]

S-H:

Hi can someone help me with this question, thank you!


The curve y=ax^3+bx^2+c passes throught the points (-1,0) and (0,5). If the tangent to the curve at the point x=1 is parallel to the x-axis, find the values of a, b and c.

y=ax^3+bx^2+c

x=0 , y=5
=> c = 5

x= -1 , y=0
0 = -a+b+c
=> a - b = 5 -----(1)

dy/dx = 3ax^2 + 2bx

At x=1 , dy/dx = 0

3a + 2b = 0 -----(2)

Solving equations (1) and (2) ,

a = 2

b = -3

[S-H]

Thank you jieheng!

[S-H]

Hi Jieheng, I have one more question to ask:-


A woman invested an amount of money in a firm and earned a simple interest of $54 each year. In a certain year when the company was not performing well, the interest rate was decreased by 0.25%, and the annual interest received dropped to $47.20. How much money did she invest?

Thanks in advance!

[archie2]

can someone help with this question

Q>> a bag contains 200 marbles. there are 60 red, 60 blue, 60 green and the remaining 20 consists of some yellow and white. If marbles are chosen from the bag without looking, what is the smallest number of marbles one must pick in order to ensure that, among the chosen marbles, at least 20 are of the same colour?

[S-H]

quekcc:

S-H:

Hi Jieheng, I have one more question to ask:-


A woman invested an amount of money in a firm and earned a simple interest of $54 each year. In a certain year when the company was not performing well, the interest rate was decreased by 0.25%, and the annual interest received dropped to $47.20. How much money did she invest?

Thanks in advance!

The drop in interest received is $54-$47.2 = $6.8

which is equal to the amount invested $y x drop in interest rate

So 0.25% y = $6.8 ------> y = $2720

Thanks quekcc!