1.

There are 7 girls on a bus and each girl has 7backpacks. In each backpack, there are 7 big cats,for every big cat, there are 7 kittens on bus. Howmany legs are on the bus, not counting the driver?1. 10,0002. 11,0003. 10,9904. 9,990​

Answer»

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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