the use of letters to substitute unknown numbers to form an equation. solve the equation to get the unknown number using different methods such as simultaneous equations and more.

306,363 questions

there is a bus with 7 children inside. each child has 7 bags. inside each bag there are 7 big cats. each big cat has 7 small cats. all cats have 4 legs each. how many legs are on the bus ?

as a riddle, the answer is zero legs on the bus since the bus has wheels instead of legs.

but as a maths problem; it's not a tricked question -- just a straightforward maths problem

confirmed answer is 10990 legs.

§ let's say the whole situation simply :

- there are 7 girls.

- each girl has 7 backpack

- each backpack has 7 big cats

- each big cat has 7 little small cats.

§ question: how many legs are there in the bus?

§ let's focus on each part of the question systematically, write down on a piece of paper if you have to, following my steps of chains.

1. focus on the first girl first:

a b c d e f g

girl a has 7 backpacks

2. now focus on first backpack a1 :

a1 a2 a3 a4 a5 a6 a7

backpack a1 has 7 big cats

3. now focus on first big cat :

1 2 3 4 5 6 7

ø each big cats have 7 small cats (that's the end of the focus)

systematically, 7 small cats has 28 legs (7 * 4) combined with the big cat that owns this 7 small cats.

let's call this the "cat chain", so cat chain 1 has 32 legs altogether.

ø so since there are 7 big cats

7 * 32 = 224 legs

ø therefore each backpack has 224 legs

ø finally, each girl has 7 * 224 = 1568 legs.

lastly, since there are 7 girls, a to g, there are 7 * 1568 legs (per girl) = 10976 legs.

now, since each girl also has 2 legs each;

so, ( 7 * 2) + 10976 = 10990 legs altogether

note: disregarding bus driver, buses and etc…only focus on the girl and their backpacks!


there are 7*7 = 49 bags and there are 7 + 7*7 = 56 cats in each bag, meaning there are 56*4 = 224 legs in each bag. so including the 7 children that have 2 legs each, there are 7*2 + 49(224) = 10990 legs in total.

which one is bigger 7g or 698 mg ?

since one gram (g) equals 1,000 milligrams (mg) 7 grams is the same as 7,000 milligrams, which is larger than 698 milligrams.

solution for square root of 2.5 ?

that is equivalent to the (square root of 5) over the (square root of 2). multiplying numerator and denominator by (square root of 2), this can be simplified to (square root of 10) / 2.

there is a way to calculate the square root of any number with a pencil and paper. it

looks a lot like long division on the paper, and it's not much harder than long division,

but it's too complex to describe here. until you learn it, your best bet is to get your

square roots with a calculator, a computer, or a slide rule.

the square root of 2.5 is 1.581138830084189665999446772216(rounded).

how many 3s are in 83333333333333333333333333333 ?

there are 29 3s because there also a 3 in the how many 3s are in 83333333333333333333333333333

decrease 20 cm by 20 mm ?

first convert to the same unit (1 cm = 10 mm). then do the subtraction.

does google plex equal infinity ?

furthermore, no number is equal to infinity because infinity is not a number, it is a concept, so theoretically, no number could be equal to it.

is 0.75 bigger or smaller than 0.8 ?

smaller. if you have trouble understanding that, then pad out 0.8 with an extra zero and make it 0.80. that is the same thing. thus 0.75 is smaller than 0.80.

what is the word form for 0.000001 ?

the term is written as "one millionth." as a prefix in si measurements it is "micro". for example, 0.000001 grams is the same as 1 microgram. 0.000001 metres is called a micrometer but also has the special name "micron".

sometimes expressed as "zero point zero zero zero zero zero one"

what is 40 cubed ?

to cube a number means simply to multiply that number by itself 3 times. to work out 40 cubed you would simply go:

403 = 40 x 40 x 40

40 x 40 = 1,600

1,600 x 40 = 64,000


therefore, 40 cubed equals 64,000.

the phrase "multiply that number by itself 3 times." can cause confusion.

sometimes, instead of multiplying it thrice (the number itself) others, due to confusion, just multiply the number by 3... take note it's cube...

what do you get if you multiply 40 by itself once?

nearly everyone would say 1,600 which is 40².

multiply that by 40 then seems to mean multiply the answer by 40, giving 64,000 which is then 40 multiplied by itself twice!

of course some people will say it doesn't matter how many times you multiply 40 by itself you'll always get 1,600.

just think of 40³ as meaning 3 40s multiplied together and you should avoid any problems.

what instrument measures angles ?

a protractor is a circular or semi circular instrument for measuring angles and some have existed from ancient times. a half circular protractor is marked for 180 degrees and a full circle for 360 degrees. protractors usually have two sets of numbers going in opposite directions, so be careful which side you use. when in doubt you should ask yourself is the angle greater or smaller that 90 degrees.

what is the whole number 8 over 1 ?

it means 8 divided by 1. and anything divided by 1 is itself!

how many periods an 8 digit number has ?


the key to answering this question is knowing what the mathematical term "period" means.

period : a period is each group of digits separated by commas in a multidigit number.

example: 30,149,258 is an 8 digit number so each part of the number separated by a comma is 1 period. {30}{149}{258}

i hope this helped.

1.7 equls how many tenths ?

none. "tenths" means there are ten, but since you are starting with almost two, it doesn't add up.

how much tonnage air conditioner is required for 2779 sq ft ?

it depends a great deal on where you live and how well your home is insulated. square feet is not a great help when planning the size of an air conditioner. it is very useful to also have the cubic feet in the home, along with the sizes and types of windows.

where i live in the northwest us, a 3-ton unit would do the trick easily, but then, we do not get the intensely hot, long summers as you might in say, phoenix.

what are the shared prime factors of 36 and 144 ?

2 and 3. in fact, 2 and 3 are the only prime factors of both.

36 = 22 x 32.

144 = 24 x 32.

find the sum of the opposite of -18 and its additive inverse ?

the additive inverse of -18 is +18.

hence if you want to add them,

remember the additive inverse of a negative number will be its positive.

its simple, just remove the negativity symbol. so -5 additive inverse is +5.

and for a positive number just put a negativity symbol in front of it. :d.

hence +10 will become -10.

remember the additive inverses always add up to give zero!!

therefore you can always use this way to find the answer of your question.

let the additive inverse of -18 be x.

as the law states, they add up to 0

-18 + x = 0

x = 0- (-18)

x = 0+18

x = 18

coming to the next part of your question,

the opposite of -18 is simply the additive inverse!!!

therefore its 18!!



hope that helps buddy!!