Q&A - P4 Math

[Thein]

You are most welcome AgonyMum

[ttyh]

Need help…

1) Figure out a formula that tells the sum of all the whole numbers between any 2 whole numbers. Show how you did it? What is the sum of all numbers between 1000 and 2000?
Thanks

[tianzhu]

ttyh:

Need help...

1) Figure out a formula that tells the sum of all the whole numbers between any 2 whole numbers. Show how you did it? What is the sum of all numbers between 1000 and 2000?
Thanks

Hi

Good Morning.

This is similar to a regular question in primary school maths.

Find the sum of the first 100 whole numbers.

First thing first, do you intend to include 1000 and 2000 in your calculations?

You’ve used “between 1000 and 2000”, this signals that you intended to have the sum of numbers from 1001 to 1999.

Actually, you don’t need any formula.

Write the sequence \"forward and backwards”

1001 + 1002 ------------------- 1999
1999 + 1998 ------------------- 1001

Add vertically

3000 + 3000 -------------------- 3000

This is twice the sum.

The number of terms/integers is 999.

Hence the answer is 999(3000)/2 -------- 1498500

Best wishes

[ttyh]

Thanks Tian Zhu

But the question specifically asked to figure out a formula…how?

[MathIzzzFun]

ttyh:

Thanks Tian Zhu

But the question specifically asked to figure out a formula....how?

Hi

sum
= (number of terms) * average of (1st term + last term)
= (number of terms) * (1st term + last term)/2


cheers.

[ozora]

need some guide on the following question.

Sue and Shaq spend $95 altogether. If Sue spent $15 less, she would have spent thrice as much Shaq. How much did Sue spend?
Is it $75?

[MathIzzzFun]

ozora:

need some guide on the following question.

Sue and Shaq spend $95 altogether. If Sue spent $15 less, she would have spent thrice as much Shaq. How much did Sue spend?
Is it $75?

:boogie: :boogie: :boogie:

cheers.

[AgonyMum]

Hi,can anyone show me the proper working for these Fractions questions.

TIA!

1) Doreen is 3 times as old as her daughter now. If her daughter’s age is 2/3 of her age in 30 years’ time, how old is Doreen now?

2) Winnie, Xavier and Yonda had a total of $407.50. Xavier had $20 lesss than Yonda.Yonda ahd 2/5 the amount of money Winnie had. How much money did Xavier have?

3) The total mass of Johnny and Alex was 180kg.After going through a weight-loss prog, Johnny lost 2/5 of this original mass while Alex lost 20 kg. They have the same mass now. What was Alex’s mass before he joined the prog?

[MathIzzzFun]

AgonyMum:

Hi,can anyone show me the proper working for these Fractions questions.

TIA!

1) Doreen is 3 times as old as her daughter now. If her daughter's age is 2/3 of her age in 30 years' time, how old is Doreen now?

Hi


for questions on age, the key concept is \"same gap/difference\" since age difference/gap remains the same.

Now,
Doreen's age --> 3 units }
Daughter's age --> 1 unit } (gap 2 units)

In 30 years' time,
Daughter's age = 2/3 Doreen's age = 4/6 Doreen's age (gap of 2)
ie
Doreen's age --> 6 units
Daughter's age --> 4 units

So, 6 units - 3 units = 30 years
1 unit --> 10 years, 3 units --> 30

Doreen is 30 years old now.

You can replace the units with blocks for MD.

cheers.

[MathIzzzFun]

AgonyMum:

Hi,can anyone show me the proper working for these Fractions questions.

TIA!



2) Winnie, Xavier and Yonda had a total of $407.50. Xavier had $20 lesss than Yonda.Yonda ahd 2/5 the amount of money Winnie had. How much money did Xavier have?

Hi

Winnie --> 5 units
Yonda --> 2 units
Xavier --> 2 units - $20
Total : 9 units - $ 20 = $407.50
1 unit --> $47.50
Xavier --> $75

For MD, replace the units with blocks.

cheers.