Question

There are 7 girls on a bus and each girl has 7
backpacks. In each backpack, there are 7 big cats,
for every big cat, there are 7 kittens on bus. How
many legs are on the bus, not counting the driver?
1. 10,000
2. 11,000
3. 10,990
4. 9,990​

Answer 1

Given data:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎There are 7 girls on a bus and each girl has 7 backpacks. In each backpack, there are 7 big cats. For every big cat, there are 7 kittens. How many legs are on the bus, excluding the driver.

Solution:

First let's list out the organisms in the bus.

• Driver
• Girls
• Big cats
• Kittens

In the data, we are said that the number of legs of the driver shouldn't be counted. So, we shall ignore the driver.

It is given that there are 7 girls on the bus. Since humans have 2 legs, there are:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{7(2)=\bf{14\:legs}}$ (in the girls group).

Now, heading towards the big cats, it is given that each girl has 7 backpacks and in each backpack, there are 7 big cats. So, the number of backpacks in the bus is:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎$\dashrightarrow\sf{7(7)=49}$

Since there are 7 big cats in each backpack, the total number of big cats is:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎$\dashrightarrow\sf{49(7)=343}$

A big cat has 4 legs. So, the total number of legs in big cats group is:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{343(4)=\bf{1372\: legs}}$

As per the data, each big cat has 7 kittens. Hence, the number of kittens, 343 big cats has is:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎$\dashrightarrow\sf{343(7)=2401}$

We know big cats have 4 legs, their kittens will also have 4 legs and as a result, there are:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{2401(4)=\bf{9604\: legs}}$ (in the kittens group).

Finally, on summing up the total number of legs in each group gives the required answer, i.e.,

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{14+1372+9604}$

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{1386+9604}$

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\underline{\boxed{\bf{\red{10990}}}}$

‎

✦ Therefore, there are 10,990 legs on the bus, excluding the count of driver's legs. Hence, option (3) is correct.

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Answer 2

$\underline{\underline{\huge{\blue{\tt{\textbf Answer :-}}}}}$

First let's list out the organisms in the bus.

• Driver
• Girls
• Big cats
• Kittens

In the data, we are said that the number of legs of the driver shouldn't be counted. So, we shall ignore the driver.

It is given that there are 7 girls on the bus. Since humans have 2 legs, there are:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{7(2)=\bf{14\:legs}}$ (in the girls group).

Now, heading towards the big cats, it is given that each girl has 7 backpacks and in each backpack, there are 7 big cats. So, the number of backpacks in the bus is:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎$\dashrightarrow\sf{7(7)=49}$

Since there are 7 big cats in each backpack, the total number of big cats is:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎$\dashrightarrow\sf{49(7)=343}$

A big cat has 4 legs. So, the total number of legs in big cats group is:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{343(4)=\bf{1372\: legs}}$

As per the data, each big cat has 7 kittens. Hence, the number of kittens, 343 big cats has is:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎$\dashrightarrow\sf{343(7)=2401}$

We know big cats have 4 legs, their kittens will also have 4 legs and as a result, there are:

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{2401(4)=\bf{9604\: legs}}$ (in the kittens group).

Finally, on summing up the total number of legs in each group gives the required answer, i.e.,

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{14+1372+9604}$

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\sf{1386+9604}$

‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎‎ ‎ ‎$\dashrightarrow\underline{\boxed{\bf{\red{10990}}}}$

‎

✦ Therefore, there are 10,990 legs on the bus, excluding the count of driver's legs. Hence, option (3) is correct.

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