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                                                                     EXHIBIT 4.7

                              METHANEX CORPORATION

                       PRO FORMA EARNINGS COVERAGE RATIOS

        FOR THE TWELVE MONTHS ENDED DECEMBER 31, 2001 AND MARCH 31, 2002

<Table>
<Caption>
                                                                 TWELVE         TWELVE
                                                                 MONTHS         MONTHS
                                                                 ENDED          ENDED
                                                              DECEMBER 31,    MARCH 31,
                                                                  2001           2002
                                                              ------------   ------------
                                                                (THOUSANDS OF DOLLARS)
<S>                                                           <C>            <C>
INTEREST REQUIREMENTS:
Interest expense per financial statements...................    $ 31,849       $ 30,358
Add: capitalized interest...................................       1,038          2,538
                                                                --------       --------
Interest including capitalized interest.....................      32,887         32,896
Deduct:
  Interest on US$150 million unsecured long-term debt to be
     repaid from proceeds (7.4%)............................     (11,100)       (11,100)
  Amortization of deferred financing........................        (271)          (271)
  Amortization of discount..................................        (104)          (104)
Add:
  Interest on US$200 million unsecured long-term debt
     (8.75%)(1).............................................      17,500         17,500
  Amortization of commission(1).............................         300            300
  Amortization of servicing costs(1)........................         100            100
                                                                --------       --------
Pro forma interest expense..................................    $ 39,312       $ 39,321
                                                                ========       ========
EARNINGS:
Net income..................................................    $ 71,418       $(14,737)
Add:
  Income tax expense........................................      29,347          2,145
  Interest expense..........................................      31,848         30,358
                                                                --------       --------
Earnings before interest on long-term debt and income
  taxes.....................................................    $132,613       $ 17,766
                                                                ========       ========
Earnings coverage ratio.....................................        3.37             --
                                                                ========       ========
Earnings coverage deficiency................................          --       $ 21,555
SUPPLEMENTARY CALCULATION:
Earnings before interest on long-term debt and income taxes
  (above)...................................................    $132,613       $ 17,766
Depreciation and amortization...............................     113,719        114,312
                                                                --------       --------
Earnings before depreciation, amortization, interest on
  long-term debt and income taxes...........................    $246,332       $132,078
                                                                ========       ========
Supplementary earnings coverage ratio.......................        6.27           3.36
                                                                ========       ========
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(1) Estimated amounts only. Actual amounts may differ.