Mo^.t quan tie^`n to^'t mang ddi,
Na`ng mua nhu+~ng gi` ma` ti'nh cha(?ng ra?
Thoa.t tie^n mua ba tie^`n ga`,
Tie^`n ru+o+~i ga.o ne^'p vo+'i ba ddo^`ng tra^`u\.
Tro+? la.i mua sa'u ddo^`ng cau,
Tie^`n ru+o+~i mie^'ng thi.t, gia' rau mu+o+`i ddo^`ng.
Co' gi` ma` ti'nh cha(?ng tho^ng.
Tie^`n ru+o+~i ga.o te?, sa'u ddo^`ng tra` tu+o+i\.
Ba mu+o+i ddo^`ng ru+o+.u, cha`ng o+i,
Ba mu+o+i ddo^`ng ma^.t, hai mu+o+i ddo^`ng “va`ng”.
Hai che'n nu+o+'c ma('m ro~ ra`ng,
Hai ba?y mu+o+`i bo^'n ke?o cha`ng ho^` nghi\.
Ha(m mo^'tt ddo^`ng boa^`t na^'u che`,
Mu+o+`i ddo^`ng na?i chuo^'i, cha(~n thi` Mo^.t Quan!
(Phong Dao)

Ba` chu? nha` cu?a to^i gio+ mo^.t ngo'n tay, du+' du+' ve^` phi'a to^i:
- O^ng Gia`! Sao to^i ti'nh hoa`i kho^ng ra ba ca'i tie^`n cho+. na`y?
To^i le^~ phe'p:
- Tie^`n cho+. gi`, thu+a ba`!
Ba? no'i ngay:
- Thi` ca'i “chie^.ng” ti'nh tie^`n cho+. Te^'t trong mo^.t quan tie^`n nga`y xu+a ddo'!
To^i u+` a`o:
- Va^.y\.
- Co`n va^.y gi` nu+~a, cha no^.i! Ti'nh giu`m to^i ddi\. To^i ti'nh hoa`i dda^u co' ra con so^' to^?ng co^.ng la` 600 ddo^`ng?
- Ba` ti'nh ra sao?
- Thi` ddu'ng nhu+ trong “sa'ch” a`
- Ba` la`m o+n ti'nh cho to^i nghe ddu+o+.c ho^n?
Ba? qua('c ma('t:
- DDu+o+.c chu+' sao kho^ng? Ne`:

thoa.t tie^n mua 3 tie^`n ga`, vi. chi la`  tie^`n ru+o+~i ga.o ne^'p vo+'i 3 ddo^`ng tra^`u  tro+? la.i mua 6 ddo^`ng cau tie^`n ru+o+~i mie^'ng thi.t  gia' rau 10 ddo^`ng tie^`n ru+o+~i ga.o te?  6 ddo^`ng tra` tu+o+i  30 ddo^`ng ru+o+.u cha`ng o+i  30 ddo^`ng ma^.t  20 ddo^`ng “va`ng”  2 che'n nu+o+'c ma('m,  2 X 7 =  21 ddo^`ng bo^.t na^'u che`  10 ddo^`ng na?i chuo^'i

30 ddo^`ng 15 ddo^`ng 03 ddo^`ng 06 ddo^`ng 15 ddo^`ng 10 ddo^`ng 15 ddo^`ng 06 ddo^`ng 30 ddo^`ng 30 ddo^`ng 20 ddo^`ng 14 ddo^`ng 21 ddo^`ng 10 ddo^`ng

la`m sao ra cha(~n thi` 1 quan, tu+'c 600 ddo^`ng? Kho^ng tin o^ng thu+? ma^`n ba`i toa'n co^.ng coi, 
pha?i to^?ng so^' chi? la` 225 ddo^`ng?
To^i vui ve?:
- Thu+a ba`, ba` ti'nh nhu+ va^.y, mo^.t tie^`n chi? co' 10 ddo^`ng tho^i sao?
- Cho+' kho^ng pha?i sao?
To^i la('c dda^`u:
- DDu'ng ra mo^.t tie^`n co' 60 ddo^`ng la^.n!
Ba` chu? tro+.n ma('t:
- Chu choa, mo^.t tie^`n la` 60 ddo^`ng sao?
To^i ga^.t dda^`u:
- Da. ddu'ng va^.y, thu+a ba`!
- Va^.y dde^? tui la^'y ca'i ma'y ti'nh coi, ma` tui pha?i ddo.c la.i mo+'i nho+' ddu+o+.c:

Mo^.t quan tie^`n to^'t mang ddi,
Na`ng mua nhu+~ng gi` ma` ti'nh cha(?ng ra?

Thoa.t tie^n mua ba tie^`n ga`, tu+'c la`  Tie^`n ru+o+~i ga.o ne^'p vo+'i ba ddo^`ng tra^`u\.  90 + 03  Tro+? la.i mua sa'u ddo^`ng cau,        6 ddo^`ng Tie^`n ru+o+~i mie^'ng thi.t, gia' rau mu+o+`i ddo^`ng. 90 + 10  Co' gi` ma` ti'nh cha(?ng tho^ng. Tie^`n ru+o+~i ga.o te?, sa'u ddo^`ng tra` tu+o+i\. 90 + 6  Ba mu+o+i ddo^`ng ru+o+.u, cha`ng o+i,  Ba mu+o+i ddo^`ng ma^.t, hai mu+o+i ddo^`ng “va`ng”. 30 + 20  Hai che'n nu+o+'c ma('m ro~ ra`ng, Hai ba?y mu+o+`i bo^'n ke?o cha`ng ho^` nghi\.  2 X 7  Ha(m mo^'t ddo^`ng bo^.t na^'u che`,  Mu+o+`i ddo^`ng na?i chuo^'i, cha(~n thi` Mo^.t Quan!

180 ddo^`ng 93 ddo^`ng 6 ddo^`ng 100 ddo^`ng 96 ddo^`ng 30 ddo^`ng 50 ddo^`ng 14 ddo^`ng 21 ddo^`ng 10 ddo^`ng

DDe^? tui to^?ng co^.ng coi a` o+` ho+' ddu'ng la` 600 ddo^`ng, co' va^.y ma` tui ti'nh ho^?ng ra!
 

Hoa`ng Ngo.c Lie^n