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Question

Quantitative Aptitude Question on Number Systems

For any natural Number 'n', let an be the largest number not exceeding n\sqrt{n} , then a1 + a2 + a3... +a50 =

Answer

Let ana_n be the largest integer not exceeding n\sqrt{n}.
We want to compute n=150an\sum_{n=1}^{50} a_n.
We can find the values of ana_n for n=1,,50n=1, \dots, 50:
a1=1a_1 = 1
a2=1a_2 = 1
a3=1a_3 = 1
a4=2a_4 = 2
a5=2a_5 = 2
a6=2a_6 = 2
a7=2a_7 = 2
a8=2a_8 = 2
a9=3a_9 = 3
...
a49=7a_{49} = 7
a50=7a_{50} = 7
We can group the terms as follows:
an=ka_n = k if k2n<(k+1)2k^2 \le n < (k+1)^2.
The number of times kk appears in the sum is (k+1)2k2=2k+1(k+1)^2 - k^2 = 2k+1.
We want to find the largest integer kk such that k250k^2 \le 50.
72=49507^2 = 49 \le 50 and 82=64>508^2 = 64 > 50.
Thus, the largest integer kk is 7.
The values of ana_n range from 1 to 7.
The number of times kk appears in the sum is (k+1)2k2=2k+1(k+1)^2 - k^2 = 2k+1 for k=1,,7k=1, \dots, 7.
The number of times 1 appears is 2(1)+1=32(1)+1 = 3.
The number of times 2 appears is 2(2)+1=52(2)+1 = 5.
The number of times 3 appears is 2(3)+1=72(3)+1 = 7.
The number of times 4 appears is 2(4)+1=92(4)+1 = 9.
The number of times 5 appears is 2(5)+1=112(5)+1 = 11.
The number of times 6 appears is 2(6)+1=132(6)+1 = 13.
The number of times 7 appears is 5049+1=250 - 49 + 1 = 2.
The sum is:
n=150an=1(3)+2(5)+3(7)+4(9)+5(11)+6(13)+7(2)=3+10+21+36+55+78+14=217\sum_{n=1}^{50} a_n = 1(3) + 2(5) + 3(7) + 4(9) + 5(11) + 6(13) + 7(2) = 3 + 10 + 21 + 36 + 55 + 78 + 14 = 217.
Final Answer: The final answer is 217\boxed{217}

Explanation

Solution

Let ana_n be the largest integer not exceeding n\sqrt{n}.
We want to compute n=150an\sum_{n=1}^{50} a_n.
We can find the values of ana_n for n=1,,50n=1, \dots, 50:
a1=1a_1 = 1
a2=1a_2 = 1
a3=1a_3 = 1
a4=2a_4 = 2
a5=2a_5 = 2
a6=2a_6 = 2
a7=2a_7 = 2
a8=2a_8 = 2
a9=3a_9 = 3
...
a49=7a_{49} = 7
a50=7a_{50} = 7
We can group the terms as follows:
an=ka_n = k if k2n<(k+1)2k^2 \le n < (k+1)^2.
The number of times kk appears in the sum is (k+1)2k2=2k+1(k+1)^2 - k^2 = 2k+1.
We want to find the largest integer kk such that k250k^2 \le 50.
72=49507^2 = 49 \le 50 and 82=64>508^2 = 64 > 50.
Thus, the largest integer kk is 7.
The values of ana_n range from 1 to 7.
The number of times kk appears in the sum is (k+1)2k2=2k+1(k+1)^2 - k^2 = 2k+1 for k=1,,7k=1, \dots, 7.
The number of times 1 appears is 2(1)+1=32(1)+1 = 3.
The number of times 2 appears is 2(2)+1=52(2)+1 = 5.
The number of times 3 appears is 2(3)+1=72(3)+1 = 7.
The number of times 4 appears is 2(4)+1=92(4)+1 = 9.
The number of times 5 appears is 2(5)+1=112(5)+1 = 11.
The number of times 6 appears is 2(6)+1=132(6)+1 = 13.
The number of times 7 appears is 5049+1=250 - 49 + 1 = 2.
The sum is:
n=150an=1(3)+2(5)+3(7)+4(9)+5(11)+6(13)+7(2)=3+10+21+36+55+78+14=217\sum_{n=1}^{50} a_n = 1(3) + 2(5) + 3(7) + 4(9) + 5(11) + 6(13) + 7(2) = 3 + 10 + 21 + 36 + 55 + 78 + 14 = 217.
Final Answer: The final answer is 217\boxed{217}