MathSolver94 wrote: Adam has RM2010 in his bank account. He donates RM10 to charity every day. His first donation is on Monday. On what day will he donate his last RM10? Do you mean looking mod $7?$ Then we have after $201$ times a Friday.

SCP wrote: MathSolver94 wrote: Adam has RM2010 in his bank account. He donates RM10 to charity every day. His first donation is on Monday. On what day will he donate his last RM10? Do you mean looking mod $7?$ Then we have after $201$ times a Friday. Could you teach me more about the mod things. I only know a little about it. Moreover, the national olympiad doesnt require the contestants to know about the modulo stuff, so I was not teached in advanced.

MathSolver94 wrote: SCP wrote: MathSolver94 wrote: Adam has RM2010 in his bank account. He donates RM10 to charity every day. His first donation is on Monday. On what day will he donate his last RM10? Do you mean looking mod $7?$ Then we have after $201$ times a Friday. Could you teach me more about the mod things. I only know a little about it. Moreover, the national olympiad doesnt require the contestants to know about the modulo stuff, so I was not teached in advanced. after each 7 times we have the same day, so after $196$ days we have again Monday when he has $1970$ and Friday then $2010RM.$

Sorry for not making clear my statement. I mean the whole modulo things, like congruence and somethings like that.

Modulo is basically the remainder when an integer is divided by another integer. Example: $9 \mod 4 = 1$ Two integers $a,b$ are congruent modulo $n$ if their remainders when divided by $n$ are equal. For example, $9 \equiv 5 \mod 4$ In this problem, there are RM2010. RM10 is deposited each day. So we have 201 days. Since a week has 7 days, we need to figure out $201 \mod 7$. $201 \equiv 61 + 140$ $\equiv 61 + 7 \cdot 20$ $\equiv 61 \mod 7$ $\equiv 5 + 56$ $\equiv 5 + 7 \cdot 8$ $\equiv 5 \mod 7$ Since the day before his first deposit was Sunday, then adding five days to Sunday gives us the answer Friday.

$\frac{2010}{10}-1\equiv 200\equiv -3\pmod{7}$. Friday is $3$ days before Monday so it is the answer.