In the house of 9 floors and several entrances. On each floor in each stairwell on 4 apartments. On what floor to be apartment No. 154?

1) 9*4=36 (apartments in each stairwell) 2) 154:36=4.2(7) (the number nonintegral, means 154 quarter is in the 5th stairwell; 1p 1-36kv., 2p 37-72kv., 3p 73-108kv., 4p 109-144kv., 5p 145-180kv.) 3) 154-144=10 (154 apartment 10th on the account in the 5th stairwell) 4) 10:4=2.5 (the number nonintegral, more than 2, means 154 quarter is on the 3rd floor of the 5th entrance)
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